] <p>If case_insensitivity is TRUE, comparison is case
     *                                     insensitive.</p>
     * @param string   $encoding           [optional] <p>Set the charset for e.g. "mb_" function</p>
     *
     * @psalm-pure
     *
     * @return int
     *             <strong>&lt; 0</strong> if str1 is less than str2;<br>
     *             <strong>&gt; 0</strong> if str1 is greater than str2,<br>
     *             <strong>0</strong> if they are equal
     */
    public static function substr_compare(
        string $str1,
        string $str2,
        int $offset = 0,
        int $length = null,
        bool $case_insensitivity = false,
        string $encoding = 'UTF-8'
    ): int {
        if (
            $offset !== 0
            ||
            $length !== null
        ) {
            if ($encoding === 'UTF-8') {
                if ($length === null) {
                    $str1 = (string) \mb_substr($str1, $offset);
                } else {
                    $str1 = (string) \mb_substr($str1, $offset, $length);
                }
                $str2 = (string) \mb_substr($str2, 0, (int) self::strlen($str1));
            } else {
                $encoding = self::normalize_encoding($encoding, 'UTF-8');

                $str1 = (string) self::substr($str1, $offset, $length, $encoding);
                $str2 = (string) self::substr($str2, 0, (int) self::strlen($str1), $encoding);
            }
        }

        if ($case_insensitivity) {
            return self::strcasecmp($str1, $str2, $encoding);
        }

        return self::strcmp($str1, $str2);
    }

    /**
     * Count the number of substring occurrences.
     *
     * EXAMPLE: <code>UTF8::substr_count('中文空白', '文空', 1, 2); // 1</code>
     *
     * @see http://php.net/manual/en/function.substr-count.php
     *
     * @param string   $haystack   <p>The string to search in.</p>
     * @param string   $needle     <p>The substring to search for.</p>
     * @param int      $offset     [optional] <p>The offset where to start counting.</p>
     * @param int|null $length     [optional] <p>
     *                             The maximum length after the specified offset to search for the
     *                             substring. It outputs a warning if the offset plus the length is
     *                             greater than the haystack length.
     *                             </p>
     * @param string   $encoding   [optional] <p>Set the charset for e.g. "mb_" function</p>
     * @param bool     $clean_utf8 [optional] <p>Remove non UTF-8 chars from the string.</p>
     *
     * @psalm-pure
     *
     * @return false|int
     *                   <p>This functions returns an integer or false if there isn't a string.</p>
     */
    public static function substr_count(
        string $haystack,
        string $needle,
        int $offset = 0,
        int $length = null,
        string $encoding = 'UTF-8',
        bool $clean_utf8 = false
    ) {
        if ($needle === '') {
            return false;
        }

        if ($haystack === '' || $length === 0) {
            return 0;
        }

        if ($encoding !== 'UTF-8' && $encoding !== 'CP850') {
            $encoding = self::normalize_encoding($encoding, 'UTF-8');
        }

        if ($clean_utf8) {
            // "mb_strpos()" and "iconv_strpos()" returns wrong position,
            // if invalid characters are found in $haystack before $needle
            $needle = self::clean($needle);
            $haystack = self::clean($haystack);
        }

        if ($offset || $length > 0) {
            if ($length === null) {
                $length_tmp = self::strlen($haystack, $encoding);
                if ($length_tmp === false) {
                    return false;
                }
                $length = $length_tmp;
            }

            if ($encoding === 'UTF-8') {
                $haystack = (string) \mb_substr($haystack, $offset, $length);
            } else {
                $haystack = (string) \mb_substr($haystack, $offset, $length, $encoding);
            }
        }

        if (
            $encoding !== 'UTF-8'
            &&
            self::$SUPPORT['mbstring'] === false
        ) {
            /**
             * @psalm-suppress ImpureFunctionCall - this is only a warning
             */
            \trigger_error('UTF8::substr_count() without mbstring cannot handle "' . $encoding . '" encoding', \E_USER_WARNING);
        }

        if (self::$SUPPORT['mbstring'] === true) {
            if ($encoding === 'UTF-8') {
                return \mb_substr_count($haystack, $needle);
            }

            return \mb_substr_count($haystack, $needle, $encoding);
        }

        \preg_match_all('/' . \preg_quote($needle, '/') . '/us', $haystack, $matches, \PREG_SET_ORDER);

        return \count($matches);
    }

    /**
     * Count the number of substring occurrences.
     *
     * @param string   $haystack <p>
     *                           The string being checked.
     *                           </p>
     * @param string   $needle   <p>
     *                           The string being found.
     *                           </p>
     * @param int      $offset   [optional] <p>
     *                           The offset where to start counting
     *                           </p>
     * @param int|null $length   [optional] <p>
     *                           The maximum length after the specified offset to search for the
     *                           substring. It outputs a warning if the offset plus the length is
     *                           greater than the haystack length.
     *                           </p>
     *
     * @psalm-pure
     *
     * @return false|int
     *                   <p>The number of times the
     *                   needle substring occurs in the
     *                   haystack string.</p>
     */
    public static function substr_count_in_byte(
        string $haystack,
        string $needle,
        int $offset = 0,
        int $length = null
    ) {
        if ($haystack === '' || $needle === '') {
            return 0;
        }

        if (
            ($offset || $length !== null)
            &&
            self::$SUPPORT['mbstring_func_overload'] === true
        ) {
            if ($length === null) {
                $length_tmp = self::strlen($haystack);
                if ($length_tmp === false) {
                    return false;
                }
                $length = $length_tmp;
            }

            if (
                (
                    $length !== 0
                    &&
                    $offset !== 0
                )
                &&
                ($length + $offset) <= 0
                &&
                \PHP_VERSION_ID < 71000 // output from "substr_count()" have changed in PHP 7.1
            ) {
                return false;
            }

            /** @var false|string $haystack_tmp - needed for PhpStan (stubs error) */
            $haystack_tmp = \substr($haystack, $offset, $length);
            if ($haystack_tmp === false) {
                $haystack_tmp = '';
            }
            $haystack = (string) $haystack_tmp;
        }

        if (self::$SUPPORT['mbstring_func_overload'] === true) {
            // "mb_" is available if overload is used, so use it ...
            return \mb_substr_count($haystack, $needle, 'CP850'); // 8-BIT
        }

        if ($length === null) {
            return \substr_count($haystack, $needle, $offset);
        }

        return \substr_count($haystack, $needle, $offset, $length);
    }

    /**
     * Returns the number of occurrences of $substring in the given string.
     * By default, the comparison is case-sensitive, but can be made insensitive
     * by setting $case_sensitive to false.
     *
     * @param string $str            <p>The input string.</p>
     * @param string $substring      <p>The substring to search for.</p>
     * @param bool   $case_sensitive [optional] <p>Whether or not to enforce case-sensitivity. Default: true</p>
     * @param string $encoding       [optional] <p>Set the charset for e.g. "mb_" function</p>
     *
     * @psalm-pure
     *
     * @return int
     *
     * @phpstan-return 0|positive-int
     */
    public static function substr_count_simple(
        string $str,
        string $substring,
        bool $case_sensitive = true,
        string $encoding = 'UTF-8'
    ): int {
        if ($str === '' || $substring === '') {
            return 0;
        }

        if ($encoding === 'UTF-8') {
            if ($case_sensitive) {
                return (int) \mb_substr_count($str, $substring);
            }

            return (int) \mb_substr_count(
                \mb_strtoupper($str),
                \mb_strtoupper($substring)
            );
        }

        $encoding = self::normalize_encoding($encoding, 'UTF-8');

        if ($case_sensitive) {
            return (int) \mb_substr_count($str, $substring, $encoding);
        }

        return (int) \mb_substr_count(
            self::strtocasefold($str, true, false, $encoding, null, false),
            self::strtocasefold($substring, true, false, $encoding, null, false),
            $encoding
        );
    }

    /**
     * Removes a prefix ($needle) from the beginning of the string ($haystack), case-insensitive.
     *
     * EXMAPLE: <code>
     * UTF8::substr_ileft('ΚόσμεMiddleEnd', 'Κόσμε'); // 'MiddleEnd'
     * UTF8::substr_ileft('ΚόσμεMiddleEnd', 'κόσμε'); // 'MiddleEnd'
     * </code>
     *
     * @param string $haystack <p>The string to search in.</p>
     * @param string $needle   <p>The substring to search for.</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>Return the sub-string.</p>
     */
    public static function substr_ileft(string $haystack, string $needle): string
    {
        if ($haystack === '') {
            return '';
        }

        if ($needle === '') {
            return $haystack;
        }

        if (self::str_istarts_with($haystack, $needle)) {
            $haystack = (string) \mb_substr($haystack, (int) self::strlen($needle));
        }

        return $haystack;
    }

    /**
     * Get part of a string process in bytes.
     *
     * @param string   $str    <p>The string being checked.</p>
     * @param int      $offset <p>The first position used in str.</p>
     * @param int|null $length [optional] <p>The maximum length of the returned string.</p>
     *
     * @psalm-pure
     *
     * @return false|string
     *                      <p>The portion of <i>str</i> specified by the <i>offset</i> and
     *                      <i>length</i> parameters.</p><p>If <i>str</i> is shorter than <i>offset</i>
     *                      characters long, <b>FALSE</b> will be returned.</p>
     */
    public static function substr_in_byte(string $str, int $offset = 0, int $length = null)
    {
        // empty string
        if ($str === '' || $length === 0) {
            return '';
        }

        // whole string
        if (!$offset && $length === null) {
            return $str;
        }

        if (self::$SUPPORT['mbstring_func_overload'] === true) {
            // "mb_" is available if overload is used, so use it ...
            return \mb_substr($str, $offset, $length, 'CP850'); // 8-BIT
        }

        return \substr($str, $offset, $length ?? 2147483647);
    }

    /**
     * Removes a suffix ($needle) from the end of the string ($haystack), case-insensitive.
     *
     * EXAMPLE: <code>
     * UTF8::substr_iright('BeginMiddleΚόσμε', 'Κόσμε'); // 'BeginMiddle'
     * UTF8::substr_iright('BeginMiddleΚόσμε', 'κόσμε'); // 'BeginMiddle'
     * </code>
     *
     * @param string $haystack <p>The string to search in.</p>
     * @param string $needle   <p>The substring to search for.</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>Return the sub-string.<p>
     */
    public static function substr_iright(string $haystack, string $needle): string
    {
        if ($haystack === '') {
            return '';
        }

        if ($needle === '') {
            return $haystack;
        }

        if (self::str_iends_with($haystack, $needle)) {
            $haystack = (string) \mb_substr($haystack, 0, (int) self::strlen($haystack) - (int) self::strlen($needle));
        }

        return $haystack;
    }

    /**
     * Removes a prefix ($needle) from the beginning of the string ($haystack).
     *
     * EXAMPLE: <code>
     * UTF8::substr_left('ΚόσμεMiddleEnd', 'Κόσμε'); // 'MiddleEnd'
     * UTF8::substr_left('ΚόσμεMiddleEnd', 'κόσμε'); // 'ΚόσμεMiddleEnd'
     * </code>
     *
     * @param string $haystack <p>The string to search in.</p>
     * @param string $needle   <p>The substring to search for.</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>Return the sub-string.</p>
     */
    public static function substr_left(string $haystack, string $needle): string
    {
        if ($haystack === '') {
            return '';
        }

        if ($needle === '') {
            return $haystack;
        }

        if (self::str_starts_with($haystack, $needle)) {
            $haystack = (string) \mb_substr($haystack, (int) self::strlen($needle));
        }

        return $haystack;
    }

    /**
     * Replace text within a portion of a string.
     *
     * EXAMPLE: <code>UTF8::substr_replace(array('Iñtërnâtiônàlizætiøn', 'foo'), 'æ', 1); // array('Iæñtërnâtiônàlizætiøn', 'fæoo')</code>
     *
     * source: https://gist.github.com/stemar/8287074
     *
     * @param string|string[] $str         <p>The input string or an array of stings.</p>
     * @param string|string[] $replacement <p>The replacement string or an array of stings.</p>
     * @param int|int[]       $offset      <p>
     *                                     If start is positive, the replacing will begin at the start'th offset
     *                                     into string.
     *                                     <br><br>
     *                                     If start is negative, the replacing will begin at the start'th character
     *                                     from the end of string.
     *                                     </p>
     * @param int|int[]|null  $length      [optional] <p>If given and is positive, it represents the length of the
     *                                     portion of string which is to be replaced. If it is negative, it
     *                                     represents the number of characters from the end of string at which to
     *                                     stop replacing. If it is not given, then it will default to strlen(
     *                                     string ); i.e. end the replacing at the end of string. Of course, if
     *                                     length is zero then this function will have the effect of inserting
     *                                     replacement into string at the given start offset.</p>
     * @param string          $encoding    [optional] <p>Set the charset for e.g. "mb_" function</p>
     *
     * @psalm-pure
     *
     * @return string|string[]
     *                         <p>The result string is returned. If string is an array then array is returned.</p>
     *
     * @template TSubstrReplace string|string[]
     * @phpstan-param TSubstrReplace $str
     * @phpstan-return TSubstrReplace
     */
    public static function substr_replace(
        $str,
        $replacement,
        $offset,
        $length = null,
        string $encoding = 'UTF-8'
    ) {
        if (\is_array($str)) {
            $num = \count($str);

            // the replacement
            if (\is_array($replacement)) {
                $replacement = \array_slice($replacement, 0, $num);
            } else {
                $replacement = \array_pad([$replacement], $num, $replacement);
            }

            // the offset
            if (\is_array($offset)) {
                $offset = \array_slice($offset, 0, $num);
                foreach ($offset as &$value_tmp) {
                    $value_tmp = (int) $value_tmp === $value_tmp ? $value_tmp : 0;
                }
                unset($value_tmp);
            } else {
                $offset = \array_pad([$offset], $num, $offset);
            }

            // the length
            if ($length === null) {
                $length = \array_fill(0, $num, 0);
            } elseif (\is_array($length)) {
                $length = \array_slice($length, 0, $num);
                foreach ($length as &$value_tmp_V2) {
                    $value_tmp_V2 = (int) $value_tmp_V2 === $value_tmp_V2 ? $value_tmp_V2 : $num;
                }
                unset($value_tmp_V2);
            } else {
                $length = \array_pad([$length], $num, $length);
            }

            // recursive call
            /** @phpstan-ignore-next-line - phpstan currently can't handle recursive calls */
            return \array_map([self::class, 'substr_replace'], $str, $replacement, $offset, $length);
        }

        if (\is_array($replacement)) {
            if ($replacement !== []) {
                $replacement = $replacement[0];
            } else {
                $replacement = '';
            }
        }

        // init
        $str = (string) $str;
        $replacement = (string) $replacement;

        if (\is_array($length)) {
            throw new \InvalidArgumentException('Parameter "$length" can only be an array, if "$str" is also an array.');
        }

        if (\is_array($offset)) {
            throw new \InvalidArgumentException('Parameter "$offset" can only be an array, if "$str" is also an array.');
        }

        if ($str === '') {
            return $replacement;
        }

        if (self::$SUPPORT['mbstring'] === true) {
            $string_length = (int) self::strlen($str, $encoding);

            if ($offset < 0) {
                $offset = (int) \max(0, $string_length + $offset);
            } elseif ($offset > $string_length) {
                $offset = $string_length;
            }

            if ($length !== null && $length < 0) {
                $length = (int) \max(0, $string_length - $offset + $length);
            } elseif ($length === null || $length > $string_length) {
                $length = $string_length;
            }

            if (($offset + $length) > $string_length) {
                $length = $string_length - $offset;
            }

            return ((string) \mb_substr($str, 0, $offset, $encoding)) .
                   $replacement .
                   ((string) \mb_substr($str, $offset + $length, $string_length - $offset - $length, $encoding));
        }

        //
        // fallback for ascii only
        //

        if (ASCII::is_ascii($str)) {
            return ($length === null) ?
                \substr_replace($str, $replacement, $offset) :
                \substr_replace($str, $replacement, $offset, $length);
        }

        //
        // fallback via vanilla php
        //

        \preg_match_all('/./us', $str, $str_matches);
        \preg_match_all('/./us', $replacement, $replacement_matches);

        if ($length === null) {
            $length_tmp = self::strlen($str, $encoding);
            if ($length_tmp === false) {
                // e.g.: non mbstring support + invalid chars
                return '';
            }
            $length = $length_tmp;
        }

        \array_splice($str_matches[0], $offset, $length, $replacement_matches[0]);

        return \implode('', $str_matches[0]);
    }

    /**
     * Removes a suffix ($needle) from the end of the string ($haystack).
     *
     * EXAMPLE: <code>
     * UTF8::substr_right('BeginMiddleΚόσμε', 'Κόσμε'); // 'BeginMiddle'
     * UTF8::substr_right('BeginMiddleΚόσμε', 'κόσμε'); // 'BeginMiddleΚόσμε'
     * </code>
     *
     * @param string $haystack <p>The string to search in.</p>
     * @param string $needle   <p>The substring to search for.</p>
     * @param string $encoding [optional] <p>Set the charset for e.g. "mb_" function</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>Return the sub-string.</p>
     */
    public static function substr_right(
        string $haystack,
        string $needle,
        string $encoding = 'UTF-8'
    ): string {
        if ($haystack === '') {
            return '';
        }

        if ($needle === '') {
            return $haystack;
        }

        if (
            $encoding === 'UTF-8'
            &&
            \substr($haystack, -\strlen($needle)) === $needle
        ) {
            return (string) \mb_substr($haystack, 0, (int) \mb_strlen($haystack) - (int) \mb_strlen($needle));
        }

        if (\substr($haystack, -\strlen($needle)) === $needle) {
            return (string) self::substr(
                $haystack,
                0,
                (int) self::strlen($haystack, $encoding) - (int) self::strlen($needle, $encoding),
                $encoding
            );
        }

        return $haystack;
    }

    /**
     * Returns a case swapped version of the string.
     *
     * EXAMPLE: <code>UTF8::swapCase('déJÀ σσς iıII'); // 'DÉjà ΣΣΣ IIii'</code>
     *
     * @param string $str        <p>The input string.</p>
     * @param string $encoding   [optional] <p>Set the charset for e.g. "mb_" function</p>
     * @param bool   $clean_utf8 [optional] <p>Remove non UTF-8 chars from the string.</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>Each character's case swapped.</p>
     */
    public static function swapCase(string $str, string $encoding = 'UTF-8', bool $clean_utf8 = false): string
    {
        if ($str === '') {
            return '';
        }

        if ($clean_utf8) {
            // "mb_strpos()" and "iconv_strpos()" returns wrong position,
            // if invalid characters are found in $haystack before $needle
            $str = self::clean($str);
        }

        if ($encoding === 'UTF-8') {
            return (string) (\mb_strtolower($str) ^ \mb_strtoupper($str) ^ $str);
        }

        return (string) (self::strtolower($str, $encoding) ^ self::strtoupper($str, $encoding) ^ $str);
    }

    /**
     * Checks whether symfony-polyfills are used.
     *
     * @psalm-pure
     *
     * @return bool
     *              <p><strong>true</strong> if in use, <strong>false</strong> otherwise</p>
     *
     * @internal <p>Please do not use it anymore, we will make is private in next major version.</p>
     */
    public static function symfony_polyfill_used(): bool
    {
        // init
        $return = false;

        $return_tmp = \extension_loaded('mbstring');
        if (!$return_tmp && \function_exists('mb_strlen')) {
            $return = true;
        }

        $return_tmp = \extension_loaded('iconv');
        if (!$return_tmp && \function_exists('iconv')) {
            $return = true;
        }

        return $return;
    }

    /**
     * @param string $str
     * @param int    $tab_length
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function tabs_to_spaces(string $str, int $tab_length = 4): string
    {
        if ($tab_length === 4) {
            $spaces = '    ';
        } elseif ($tab_length === 2) {
            $spaces = '  ';
        } else {
            $spaces = \str_repeat(' ', $tab_length);
        }

        return \str_replace("\t", $spaces, $str);
    }

    /**
     * Converts the first character of each word in the string to uppercase
     * and all other chars to lowercase.
     *
     * @param string      $str                           <p>The input string.</p>
     * @param string      $encoding                      [optional] <p>Set the charset for e.g. "mb_" function</p>
     * @param bool        $clean_utf8                    [optional] <p>Remove non UTF-8 chars from the string.</p>
     * @param string|null $lang                          [optional] <p>Set the language for special cases: az, el, lt,
     *                                                   tr</p>
     * @param bool        $try_to_keep_the_string_length [optional] <p>true === try to keep the string length: e.g. ẞ
     *                                                   -> ß</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>A string with all characters of $str being title-cased.</p>
     */
    public static function titlecase(
        string $str,
        string $encoding = 'UTF-8',
        bool $clean_utf8 = false,
        string $lang = null,
        bool $try_to_keep_the_string_length = false
    ): string {
        if ($clean_utf8) {
            // "mb_strpos()" and "iconv_strpos()" returns wrong position,
            // if invalid characters are found in $haystack before $needle
            $str = self::clean($str);
        }

        if (
            $lang === null
            &&
            !$try_to_keep_the_string_length
        ) {
            if ($encoding === 'UTF-8') {
                return \mb_convert_case($str, \MB_CASE_TITLE);
            }

            $encoding = self::normalize_encoding($encoding, 'UTF-8');

            return \mb_convert_case($str, \MB_CASE_TITLE, $encoding);
        }

        return self::str_titleize(
            $str,
            null,
            $encoding,
            false,
            $lang,
            $try_to_keep_the_string_length,
            false
        );
    }

    /**
     * Convert a string into ASCII.
     *
     * EXAMPLE: <code>UTF8::to_ascii('déjà σσς iıii'); // 'deja sss iiii'</code>
     *
     * @param string $str     <p>The input string.</p>
     * @param string $unknown [optional] <p>Character use if character unknown. (default is ?)</p>
     * @param bool   $strict  [optional] <p>Use "transliterator_transliterate()" from PHP-Intl | WARNING: bad
     *                        performance</p>
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function to_ascii(
        string $str,
        string $unknown = '?',
        bool $strict = false
    ): string {
        return ASCII::to_transliterate($str, $unknown, $strict);
    }

    /**
     * @param bool|float|int|string $str
     *
     * @psalm-pure
     *
     * @return bool
     */
    public static function to_boolean($str): bool
    {
        // init
        $str = (string) $str;

        if ($str === '') {
            return false;
        }

        // Info: http://php.net/manual/en/filter.filters.validate.php
        $map = [
            'true'  => true,
            '1'     => true,
            'on'    => true,
            'yes'   => true,
            'false' => false,
            '0'     => false,
            'off'   => false,
            'no'    => false,
        ];

        if (isset($map[$str])) {
            return $map[$str];
        }

        $key = \strtolower($str);
        if (isset($map[$key])) {
            return $map[$key];
        }

        if (\is_numeric($str)) {
            return ((float) $str) > 0;
        }

        return (bool) \trim($str);
    }

    /**
     * Convert given string to safe filename (and keep string case).
     *
     * @param string $str
     * @param bool   $use_transliterate No transliteration, conversion etc. is done by default - unsafe characters are
     *                                  simply replaced with hyphen.
     * @param string $fallback_char
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function to_filename(
        string $str,
        bool $use_transliterate = false,
        string $fallback_char = '-'
    ): string {
        return ASCII::to_filename(
            $str,
            $use_transliterate,
            $fallback_char
        );
    }

    /**
     * Convert a string into "ISO-8859"-encoding (Latin-1).
     *
     * EXAMPLE: <code>UTF8::to_utf8(UTF8::to_iso8859('  -ABC-中文空白-  ')); // '  -ABC-????-  '</code>
     *
     * @param string|string[] $str
     *
     * @psalm-pure
     *
     * @return string|string[]
     *
     * @template TToIso8859 as string|string[]
     * @phpstan-param TToIso8859 $str
     * @phpstan-return (TToIso8859 is string ? string : string[])
     */
    public static function to_iso8859($str)
    {
        if (\is_array($str)) {
            foreach ($str as &$v) {
                $v = self::to_iso8859($v);
            }

            return $str;
        }

        /* @phpstan-ignore-next-line | FP? -> "Cannot cast TToIso8859 of array<string>|string to string." it's a string here */
        $str = (string) $str;
        if ($str === '') {
            return '';
        }

        return self::utf8_decode($str);
    }

    /**
     * This function leaves UTF-8 characters alone, while converting almost all non-UTF8 to UTF8.
     *
     * <ul>
     * <li>It decode UTF-8 codepoints and Unicode escape sequences.</li>
     * <li>It assumes that the encoding of the original string is either WINDOWS-1252 or ISO-8859.</li>
     * <li>WARNING: It does not remove invalid UTF-8 characters, so you maybe need to use "UTF8::clean()" for this
     * case.</li>
     * </ul>
     *
     * EXAMPLE: <code>UTF8::to_utf8(["\u0063\u0061\u0074"]); // array('cat')</code>
     *
     * @param string|string[] $str                        <p>Any string or array of strings.</p>
     * @param bool            $decode_html_entity_to_utf8 <p>Set to true, if you need to decode html-entities.</p>
     *
     * @psalm-pure
     *
     * @return string|string[]
     *                         <p>The UTF-8 encoded string</p>
     *
     * @template TToUtf8 as string|string[]
     * @phpstan-param TToUtf8 $str
     * @phpstan-return (TToUtf8 is string ? string : string[])
     */
    public static function to_utf8($str, bool $decode_html_entity_to_utf8 = false)
    {
        if (\is_array($str)) {
            foreach ($str as &$v) {
                $v = self::to_utf8_string($v, $decode_html_entity_to_utf8);
            }

            /** @phpstan-var TToUtf8 $str */
            return $str;
        }

        \assert(\is_string($str));

        $str = self::to_utf8_string($str, $decode_html_entity_to_utf8);

        /** @phpstan-var TToUtf8 $str */
        return $str;
    }

    /**
     * This function leaves UTF-8 characters alone, while converting almost all non-UTF8 to UTF8.
     *
     * <ul>
     * <li>It decode UTF-8 codepoints and Unicode escape sequences.</li>
     * <li>It assumes that the encoding of the original string is either WINDOWS-1252 or ISO-8859.</li>
     * <li>WARNING: It does not remove invalid UTF-8 characters, so you maybe need to use "UTF8::clean()" for this
     * case.</li>
     * </ul>
     *
     * EXAMPLE: <code>UTF8::to_utf8_string("\u0063\u0061\u0074"); // 'cat'</code>
     *
     * @param string $str                        <p>Any string.</p>
     * @param bool   $decode_html_entity_to_utf8 <p>Set to true, if you need to decode html-entities.</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>The UTF-8 encoded string</p>
     *
     * @template T as string
     * @phpstan-param T $str
     * @phpstan-return (T is non-empty-string ? non-empty-string : string)
     */
    public static function to_utf8_string(string $str, bool $decode_html_entity_to_utf8 = false): string
    {
        if ($str === '') {
            return $str;
        }

        $max = \strlen($str);
        $buf = '';

        for ($i = 0; $i < $max; ++$i) {
            $c1 = $str[$i];

            if ($c1 >= "\xC0") { // should be converted to UTF8, if it's not UTF8 already

                if ($c1 <= "\xDF") { // looks like 2 bytes UTF8

                    $c2 = $i + 1 >= $max ? "\x00" : $str[$i + 1];

                    if ($c2 >= "\x80" && $c2 <= "\xBF") { // yeah, almost sure it's UTF8 already
                        $buf .= $c1 . $c2;
                        ++$i;
                    } else { // not valid UTF8 - convert it
                        $buf .= self::to_utf8_convert_helper($c1);
                    }
                } elseif ($c1 >= "\xE0" && $c1 <= "\xEF") { // looks like 3 bytes UTF8

                    $c2 = $i + 1 >= $max ? "\x00" : $str[$i + 1];
                    $c3 = $i + 2 >= $max ? "\x00" : $str[$i + 2];

                    if ($c2 >= "\x80" && $c2 <= "\xBF" && $c3 >= "\x80" && $c3 <= "\xBF") { // yeah, almost sure it's UTF8 already
                        $buf .= $c1 . $c2 . $c3;
                        $i += 2;
                    } else { // not valid UTF8 - convert it
                        $buf .= self::to_utf8_convert_helper($c1);
                    }
                } elseif ($c1 >= "\xF0" && $c1 <= "\xF7") { // looks like 4 bytes UTF8

                    $c2 = $i + 1 >= $max ? "\x00" : $str[$i + 1];
                    $c3 = $i + 2 >= $max ? "\x00" : $str[$i + 2];
                    $c4 = $i + 3 >= $max ? "\x00" : $str[$i + 3];

                    if ($c2 >= "\x80" && $c2 <= "\xBF" && $c3 >= "\x80" && $c3 <= "\xBF" && $c4 >= "\x80" && $c4 <= "\xBF") { // yeah, almost sure it's UTF8 already
                        $buf .= $c1 . $c2 . $c3 . $c4;
                        $i += 3;
                    } else { // not valid UTF8 - convert it
                        $buf .= self::to_utf8_convert_helper($c1);
                    }
                } else { // doesn't look like UTF8, but should be converted

                    $buf .= self::to_utf8_convert_helper($c1);
                }
            } elseif (($c1 & "\xC0") === "\x80") { // needs conversion

                $buf .= self::to_utf8_convert_helper($c1);
            } else { // it doesn't need conversion

                $buf .= $c1;
            }
        }

        // decode unicode escape sequences + unicode surrogate pairs
        $buf = \preg_replace_callback(
            '/\\\\u([dD][89abAB][0-9a-fA-F]{2})\\\\u([dD][cdefCDEF][\da-fA-F]{2})|\\\\u([0-9a-fA-F]{4})/',
            /**
             * @param array $matches
             *
             * @psalm-pure
             *
             * @return string
             */
            static function (array $matches): string {
                if (isset($matches[3])) {
                    $cp = (int) \hexdec($matches[3]);
                } else {
                    // http://unicode.org/faq/utf_bom.html#utf16-4
                    $cp = ((int) \hexdec($matches[1]) << 10)
                          + (int) \hexdec($matches[2])
                          + 0x10000
                          - (0xD800 << 10)
                          - 0xDC00;
                }

                // https://github.com/php/php-src/blob/php-7.3.2/ext/standard/html.c#L471
                //
                // php_utf32_utf8(unsigned char *buf, unsigned k)

                if ($cp < 0x80) {
                    return (string) self::chr($cp);
                }

                if ($cp < 0xA0) {
                    /** @noinspection UnnecessaryCastingInspection */
                    return (string) self::chr(0xC0 | $cp >> 6) . (string) self::chr(0x80 | $cp & 0x3F);
                }

                return self::decimal_to_chr($cp);
            },
            $buf
        );

        if ($buf === null) {
            return '';
        }

        // decode UTF-8 codepoints
        if ($decode_html_entity_to_utf8) {
            $buf = self::html_entity_decode($buf);
        }

        return $buf;
    }

    /**
     * Returns the given string as an integer, or null if the string isn't numeric.
     *
     * @param string $str
     *
     * @psalm-pure
     *
     * @return int|null
     *                  <p>null if the string isn't numeric</p>
     */
    public static function to_int(string $str)
    {
        if (\is_numeric($str)) {
            return (int) $str;
        }

        return null;
    }

    /**
     * Returns the given input as string, or null if the input isn't int|float|string
     * and do not implement the "__toString()" method.
     *
     * @param float|int|object|string|null $input
     *
     * @psalm-pure
     *
     * @return string|null
     *                     <p>null if the input isn't int|float|string and has no "__toString()" method</p>
     */
    public static function to_string($input)
    {
        if ($input === null) {
            return null;
        }

        $input_type = \gettype($input);

        if (
            $input_type === 'string'
            ||
            $input_type === 'integer'
            ||
            $input_type === 'float'
            ||
            $input_type === 'double'
        ) {
            /* @phpstan-ignore-next-line | "gettype" is not supported by phpstan?! */
            return (string) $input;
        }

        /** @phpstan-ignore-next-line - "gettype": FP? */
        if ($input_type === 'object' && \method_exists($input, '__toString')) {
            return (string) $input;
        }

        return null;
    }

    /**
     * Strip whitespace or other characters from the beginning and end of a UTF-8 string.
     *
     * INFO: This is slower then "trim()"
     *
     * We can only use the original-function, if we use <= 7-Bit in the string / chars
     * but the check for ASCII (7-Bit) cost more time, then we can safe here.
     *
     * EXAMPLE: <code>UTF8::trim('   -ABC-中文空白-  '); // '-ABC-中文空白-'</code>
     *
     * @param string      $str   <p>The string to be trimmed</p>
     * @param string|null $chars [optional] <p>Optional characters to be stripped</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>The trimmed string.</p>
     */
    public static function trim(string $str = '', string $chars = null): string
    {
        if ($str === '') {
            return '';
        }

        if (self::$SUPPORT['mbstring'] === true) {
            if ($chars !== null) {
                /** @noinspection PregQuoteUsageInspection */
                $chars = \preg_quote($chars);
                $pattern = "^[{$chars}]+|[{$chars}]+\$";
            } else {
                $pattern = '^[\\s]+|[\\s]+$';
            }

            return (string) \mb_ereg_replace($pattern, '', $str);
        }

        if ($chars !== null) {
            $chars = \preg_quote($chars, '/');
            $pattern = "^[{$chars}]+|[{$chars}]+\$";
        } else {
            $pattern = '^[\\s]+|[\\s]+$';
        }

        return self::regex_replace($str, $pattern, '');
    }

    /**
     * Makes string's first char uppercase.
     *
     * EXAMPLE: <code>UTF8::ucfirst('ñtërnâtiônàlizætiøn foo'); // 'Ñtërnâtiônàlizætiøn foo'</code>
     *
     * @param string      $str                           <p>The input string.</p>
     * @param string      $encoding                      [optional] <p>Set the charset for e.g. "mb_" function</p>
     * @param bool        $clean_utf8                    [optional] <p>Remove non UTF-8 chars from the string.</p>
     * @param string|null $lang                          [optional] <p>Set the language for special cases: az, el, lt,
     *                                                   tr</p>
     * @param bool        $try_to_keep_the_string_length [optional] <p>true === try to keep the string length: e.g. ẞ
     *                                                   -> ß</p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>The resulting string with with char uppercase.</p>
     */
    public static function ucfirst(
        string $str,
        string $encoding = 'UTF-8',
        bool $clean_utf8 = false,
        string $lang = null,
        bool $try_to_keep_the_string_length = false
    ): string {
        if ($str === '') {
            return '';
        }

        if ($clean_utf8) {
            // "mb_strpos()" and "iconv_strpos()" returns wrong position,
            // if invalid characters are found in $haystack before $needle
            $str = self::clean($str);
        }

        $use_mb_functions = $lang === null && !$try_to_keep_the_string_length;

        if ($encoding === 'UTF-8') {
            $str_part_two = (string) \mb_substr($str, 1);

            if ($use_mb_functions) {
                $str_part_one = \mb_strtoupper(
                    (string) \mb_substr($str, 0, 1)
                );
            } else {
                $str_part_one = self::strtoupper(
                    (string) \mb_substr($str, 0, 1),
                    $encoding,
                    false,
                    $lang,
                    $try_to_keep_the_string_length
                );
            }
        } else {
            $encoding = self::normalize_encoding($encoding, 'UTF-8');

            $str_part_two = (string) self::substr($str, 1, null, $encoding);

            if ($use_mb_functions) {
                $str_part_one = \mb_strtoupper(
                    (string) \mb_substr($str, 0, 1, $encoding),
                    $encoding
                );
            } else {
                $str_part_one = self::strtoupper(
                    (string) self::substr($str, 0, 1, $encoding),
                    $encoding,
                    false,
                    $lang,
                    $try_to_keep_the_string_length
                );
            }
        }

        return $str_part_one . $str_part_two;
    }

    /**
     * Uppercase for all words in the string.
     *
     * EXAMPLE: <code>UTF8::ucwords('iñt ërn âTi ônà liz æti øn'); // 'Iñt Ërn ÂTi Ônà Liz Æti Øn'</code>
     *
     * @param string   $str        <p>The input string.</p>
     * @param string[] $exceptions [optional] <p>Exclusion for some words.</p>
     * @param string   $char_list  [optional] <p>Additional chars that contains to words and do not start a new
     *                             word.</p>
     * @param string   $encoding   [optional] <p>Set the charset.</p>
     * @param bool     $clean_utf8 [optional] <p>Remove non UTF-8 chars from the string.</p>
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function ucwords(
        string $str,
        array $exceptions = [],
        string $char_list = '',
        string $encoding = 'UTF-8',
        bool $clean_utf8 = false
    ): string {
        if (!$str) {
            return '';
        }

        // INFO: mb_convert_case($str, MB_CASE_TITLE);
        // -> MB_CASE_TITLE didn't only uppercase the first letter, it also lowercase all other letters

        if ($clean_utf8) {
            // "mb_strpos()" and "iconv_strpos()" returns wrong position,
            // if invalid characters are found in $haystack before $needle
            $str = self::clean($str);
        }

        $use_php_default_functions = !(bool) ($char_list . \implode('', $exceptions));

        if (
            $use_php_default_functions
            &&
            ASCII::is_ascii($str)
        ) {
            return \ucwords($str);
        }

        $words = self::str_to_words($str, $char_list);
        $use_exceptions = $exceptions !== [];

        $words_str = '';
        foreach ($words as &$word) {
            if (!$word) {
                continue;
            }

            if (
                !$use_exceptions
                ||
                !\in_array($word, $exceptions, true)
            ) {
                $words_str .= self::ucfirst($word, $encoding);
            } else {
                $words_str .= $word;
            }
        }

        return $words_str;
    }

    /**
     * Multi decode HTML entity + fix urlencoded-win1252-chars.
     *
     * EXAMPLE: <code>UTF8::urldecode('tes%20öäü%20\u00edtest+test'); // 'tes öäü ítest test'</code>
     *
     * e.g:
     * 'test+test'                     => 'test test'
     * 'D&#252;sseldorf'               => 'Düsseldorf'
     * 'D%FCsseldorf'                  => 'Düsseldorf'
     * 'D&#xFC;sseldorf'               => 'Düsseldorf'
     * 'D%26%23xFC%3Bsseldorf'         => 'Düsseldorf'
     * 'Düsseldorf'                   => 'Düsseldorf'
     * 'D%C3%BCsseldorf'               => 'Düsseldorf'
     * 'D%C3%83%C2%BCsseldorf'         => 'Düsseldorf'
     * 'D%25C3%2583%25C2%25BCsseldorf' => 'Düsseldorf'
     *
     * @param string $str          <p>The input string.</p>
     * @param bool   $multi_decode <p>Decode as often as possible.</p>
     *
     * @psalm-pure
     *
     * @return string
     *
     * @template T as string
     * @phpstan-param T $str
     * @phpstan-return (T is non-empty-string ? non-empty-string : string)
     */
    public static function urldecode(string $str, bool $multi_decode = true): string
    {
        if ($str === '') {
            return '';
        }

        $str = self::urldecode_unicode_helper($str);

        if ($multi_decode) {
            do {
                $str_compare = $str;

                /**
                 * @psalm-suppress PossiblyInvalidArgument
                 */
                $str = \urldecode(
                    self::html_entity_decode(
                        self::to_utf8($str),
                        \ENT_QUOTES | \ENT_HTML5
                    )
                );
            } while ($str_compare !== $str);
        } else {
            /**
             * @psalm-suppress PossiblyInvalidArgument
             */
            $str = \urldecode(
                self::html_entity_decode(
                    self::to_utf8($str),
                    \ENT_QUOTES | \ENT_HTML5
                )
            );
        }

        return self::fix_simple_utf8($str);
    }

    /**
     * Decodes a UTF-8 string to ISO-8859-1.
     *
     * EXAMPLE: <code>UTF8::encode('UTF-8', UTF8::utf8_decode('-ABC-中文空白-')); // '-ABC-????-'</code>
     *
     * @param string $str             <p>The input string.</p>
     * @param bool   $keep_utf8_chars
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function utf8_decode(string $str, bool $keep_utf8_chars = false): string
    {
        if ($str === '') {
            return '';
        }

        // save for later comparision
        $str_backup = $str;
        $len = \strlen($str);

        if (self::$ORD === null) {
            self::$ORD = self::getData('ord');
        }

        if (self::$CHR === null) {
            self::$CHR = self::getData('chr');
        }

        $no_char_found = '?';
        for ($i = 0, $j = 0; $i < $len; ++$i, ++$j) {
            switch ($str[$i] & "\xF0") {
                case "\xC0":
                case "\xD0":
                    $c = (self::$ORD[$str[$i] & "\x1F"] << 6) | self::$ORD[$str[++$i] & "\x3F"];
                    $str[$j] = $c < 256 ? self::$CHR[$c] : $no_char_found;

                    break;

                case "\xF0":
                    ++$i;

                // no break

                case "\xE0":
                    $str[$j] = $no_char_found;
                    $i += 2;

                    break;

                default:
                    $str[$j] = $str[$i];
            }
        }

        /** @var false|string $return - needed for PhpStan (stubs error) */
        $return = \substr($str, 0, $j);
        if ($return === false) {
            $return = '';
        }

        if (
            $keep_utf8_chars
            &&
            (int) self::strlen($return) >= (int) self::strlen($str_backup)
        ) {
            return $str_backup;
        }

        return $return;
    }

    /**
     * Encodes an ISO-8859-1 string to UTF-8.
     *
     * EXAMPLE: <code>UTF8::utf8_decode(UTF8::utf8_encode('-ABC-中文空白-')); // '-ABC-中文空白-'</code>
     *
     * @param string $str <p>The input string.</p>
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function utf8_encode(string $str): string
    {
        if ($str === '') {
            return '';
        }

        /** @noinspection PhpUsageOfSilenceOperatorInspection | TODO for PHP > 8.2: find a replacement for this */
        /** @var false|string $str - the polyfill maybe return false */
        $str = @\utf8_encode($str);

        if ($str === false) {
            return '';
        }

        return $str;
    }

    /**
     * Returns an array with all utf8 whitespace characters.
     *
     * @see http://www.bogofilter.org/pipermail/bogofilter/2003-March/001889.html
     *
     * @psalm-pure
     *
     * @return string[]
     *                  An array with all known whitespace characters as values and the type of whitespace as keys
     *                  as defined in above URL
     */
    public static function whitespace_table(): array
    {
        return self::$WHITESPACE_TABLE;
    }

    /**
     * Limit the number of words in a string.
     *
     * EXAMPLE: <code>UTF8::words_limit('fòô bàř fòô', 2, ''); // 'fòô bàř'</code>
     *
     * @param string      $str        <p>The input string.</p>
     * @param int<1, max> $limit      <p>The limit of words as integer.</p>
     * @param string      $str_add_on <p>Replacement for the striped string.</p>
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function words_limit(
        string $str,
        int $limit = 100,
        string $str_add_on = '…'
    ): string {
        if (
            $str === ''
            ||
            /* @phpstan-ignore-next-line | we do not trust the phpdoc check */
            $limit <= 0
        ) {
            return '';
        }

        \preg_match('/^\\s*+(?:[^\\s]++\\s*+){1,' . $limit . '}/u', $str, $matches);

        if (
            !isset($matches[0])
            ||
            \mb_strlen($str) === (int) \mb_strlen($matches[0])
        ) {
            return $str;
        }

        return \rtrim($matches[0]) . $str_add_on;
    }

    /**
     * Wraps a string to a given number of characters
     *
     * EXAMPLE: <code>UTF8::wordwrap('Iñtërnâtiônàlizætiøn', 2, '<br>', true)); // 'Iñ<br>të<br>rn<br>ât<br>iô<br>nà<br>li<br>zæ<br>ti<br>øn'</code>
     *
     * @see http://php.net/manual/en/function.wordwrap.php
     *
     * @param string      $str   <p>The input string.</p>
     * @param int<1, max> $width [optional] <p>The column width.</p>
     * @param string      $break [optional] <p>The line is broken using the optional break parameter.</p>
     * @param bool        $cut   [optional] <p>
     *                      If the cut is set to true, the string is
     *                      always wrapped at or before the specified width. So if you have
     *                      a word that is larger than the given width, it is broken apart.
     *                      </p>
     *
     * @psalm-pure
     *
     * @return string
     *                <p>The given string wrapped at the specified column.</p>
     */
    public static function wordwrap(
        string $str,
        int $width = 75,
        string $break = "\n",
        bool $cut = false
    ): string {
        if ($str === '' || $break === '') {
            return '';
        }

        $str_split = \explode($break, $str);

        /** @var string[] $charsArray */
        $charsArray = [];
        $word_split = '';
        foreach ($str_split as $i => $i_value) {
            if ($i) {
                $charsArray[] = $break;
                $word_split .= '#';
            }

            foreach (self::str_split($i_value) as $c) {
                $charsArray[] = $c;
                if ($c === ' ') {
                    $word_split .= ' ';
                } else {
                    $word_split .= '?';
                }
            }
        }

        $str_return = '';
        $j = 0;
        $b = -1;
        $i = -1;
        $word_split = \wordwrap($word_split, $width, '#', $cut);

        $max = \mb_strlen($word_split);
        /** @noinspection PhpAssignmentInConditionInspection - is ok here */
        while (($b = \mb_strpos($word_split, '#', $b + 1)) !== false) {
            for (++$i; $i < $b; ++$i) {
                if (isset($charsArray[$j])) {
                    $str_return .= $charsArray[$j];
                    unset($charsArray[$j]);
                }
                ++$j;

                // prevent endless loop, e.g. if there is a error in the "mb_*" polyfill
                if ($i > $max) {
                    break 2;
                }
            }

            if (
                $break === $charsArray[$j]
                ||
                $charsArray[$j] === ' '
            ) {
                unset($charsArray[$j++]);
            }

            $str_return .= $break;

            // prevent endless loop, e.g. if there is a error in the "mb_*" polyfill
            if ($b > $max) {
                break;
            }
        }

        return $str_return . \implode('', $charsArray);
    }

    /**
     * Line-Wrap the string after $limit, but split the string by "$delimiter" before ...
     *    ... so that we wrap the per line.
     *
     * @param string      $str             <p>The input string.</p>
     * @param int<1, max> $width           [optional] <p>The column width.</p>
     * @param string      $break           [optional] <p>The line is broken using the optional break parameter.</p>
     * @param bool        $cut             [optional] <p>
     *                                     If the cut is set to true, the string is
     *                                     always wrapped at or before the specified width. So if you have
     *                                     a word that is larger than the given width, it is broken apart.
     *                                     </p>
     * @param bool        $add_final_break [optional] <p>
     *                                     If this flag is true, then the method will add a $break at the end
     *                                     of the result string.
     *                                     </p>
     * @param non-empty-string|null $delimiter       [optional] <p>
     *                                     You can change the default behavior, where we split the string by newline.
     *                                     </p>
     *
     * @psalm-pure
     *
     * @return string
     */
    public static function wordwrap_per_line(
        string $str,
        int $width = 75,
        string $break = "\n",
        bool $cut = false,
        bool $add_final_break = true,
        string $delimiter = null
    ): string {
        if ($delimiter === null) {
            $strings = \preg_split('/\\r\\n|\\r|\\n/', $str);
        } else {
            $strings = \explode($delimiter, $str);
        }

        $string_helper_array = [];
        if ($strings !== false) {
            foreach ($strings as $value) {
                $string_helper_array[] = self::wordwrap($value, $width, $break, $cut);
            }
        }

        if ($add_final_break) {
            $final_break = $break;
        } else {
            $final_break = '';
        }

        return \implode($delimiter ?? "\n", $string_helper_array) . $final_break;
    }

    /**
     * Returns an array of Unicode White Space characters.
     *
     * @psalm-pure
     *
     * @return string[]
     *                  <p>An array with numeric code point as key and White Space Character as value.</p>
     */
    public static function ws(): array
    {
        return self::$WHITESPACE;
    }

    /**
     * Checks whether the passed string contains only byte sequences that are valid UTF-8 characters.
     *
     * EXAMPLE: <code>
     * UTF8::is_utf8_string('Iñtërnâtiônàlizætiøn']); // true
     * //
     * UTF8::is_utf8_string("Iñtërnâtiônàlizætiøn\xA0\xA1"); // false
     * </code>
     *
     * @see          http://hsivonen.iki.fi/php-utf8/
     *
     * @param string $str    <p>The string to be checked.</p>
     * @param bool   $strict <p>Check also if the string is not UTF-16 or UTF-32.</p>
     *
     * @psalm-pure
     *
     * @return bool
     */
    private static function is_utf8_string(string $str, bool $strict = false)
    {
        if ($str === '') {
            return true;
        }

        if ($strict) {
            $is_binary = self::is_binary($str, true);

            if ($is_binary && self::is_utf16($str, false) !== false) {
                return false;
            }

            if ($is_binary && self::is_utf32($str, false) !== false) {
                return false;
            }
        }

        if (self::$SUPPORT['pcre_utf8']) {
            // If even just the first character can be matched, when the /u
            // modifier is used, then it's valid UTF-8. If the UTF-8 is somehow
            // invalid, nothing at all will match, even if the string contains
            // some valid sequences
            return \preg_match('/^./us', $str) === 1;
        }

        $mState = 0; // cached expected number of octets after the current octet
        // until the beginning of the next UTF8 character sequence
        $mUcs4 = 0; // cached Unicode character
        $mBytes = 1; // cached expected number of octets in the current sequence

        if (self::$ORD === null) {
            self::$ORD = self::getData('ord');
        }

        $len = \strlen($str);
        for ($i = 0; $i < $len; ++$i) {
            $in = self::$ORD[$str[$i]];

            if ($mState === 0) {
                // When mState is zero we expect either a US-ASCII character or a
                // multi-octet sequence.
                if ((0x80 & $in) === 0) {
                    // US-ASCII, pass straight through.
                    $mBytes = 1;
                } elseif ((0xE0 & $in) === 0xC0) {
                    // First octet of 2 octet sequence.
                    $mUcs4 = $in;
                    $mUcs4 = ($mUcs4 & 0x1F) << 6;
                    $mState = 1;
                    $mBytes = 2;
                } elseif ((0xF0 & $in) === 0xE0) {
                    // First octet of 3 octet sequence.
                    $mUcs4 = $in;
                    $mUcs4 = ($mUcs4 & 0x0F) << 12;
                    $mState = 2;
                    $mBytes = 3;
                } elseif ((0xF8 & $in) === 0xF0) {
                    // First octet of 4 octet sequence.
                    $mUcs4 = $in;
                    $mUcs4 = ($mUcs4 & 0x07) << 18;
                    $mState = 3;
                    $mBytes = 4;
                } elseif ((0xFC & $in) === 0xF8) {
                    /* First octet of 5 octet sequence.
                     *
                     * This is illegal because the encoded codepoint must be either
                     * (a) not the shortest form or
                     * (b) outside the Unicode range of 0-0x10FFFF.
                     * Rather than trying to resynchronize, we will carry on until the end
                     * of the sequence and let the later error handling code catch it.
                     */
                    $mUcs4 = $in;
                    $mUcs4 = ($mUcs4 & 0x03) << 24;
                    $mState = 4;
                    $mBytes = 5;
                } elseif ((0xFE & $in) === 0xFC) {
                    // First octet of 6 octet sequence, see comments for 5 octet sequence.
                    $mUcs4 = $in;
                    $mUcs4 = ($mUcs4 & 1) << 30;
                    $mState = 5;
                    $mBytes = 6;
                } else {
                    // Current octet is neither in the US-ASCII range nor a legal first
                    // octet of a multi-octet sequence.
                    return false;
                }
            } elseif ((0xC0 & $in) === 0x80) {

                // When mState is non-zero, we expect a continuation of the multi-octet
                // sequence

                // Legal continuation.
                $shift = ($mState - 1) * 6;
                $tmp = $in;
                $tmp = ($tmp & 0x0000003F) << $shift;
                $mUcs4 |= $tmp;
                // Prefix: End of the multi-octet sequence. mUcs4 now contains the final
                // Unicode code point to be output.
                if (--$mState === 0) {
                    // Check for illegal sequences and code points.
                    //
                    // From Unicode 3.1, non-shortest form is illegal
                    if (
                        ($mBytes === 2 && $mUcs4 < 0x0080)
                        ||
                        ($mBytes === 3 && $mUcs4 < 0x0800)
                        ||
                        ($mBytes === 4 && $mUcs4 < 0x10000)
                        ||
                        ($mBytes > 4)
                        ||
                        // From Unicode 3.2, surrogate characters are illegal.
                        (($mUcs4 & 0xFFFFF800) === 0xD800)
                        ||
                        // Code points outside the Unicode range are illegal.
                        ($mUcs4 > 0x10FFFF)
                    ) {
                        return false;
                    }
                    // initialize UTF8 cache
                    $mState = 0;
                    $mUcs4 = 0;
                    $mBytes = 1;
                }
            } else {
                // ((0xC0 & (*in) != 0x80) && (mState != 0))
                // Incomplete multi-octet sequence.
                return false;
            }
        }

        return $mState === 0;
    }

    /**
     * @param string $str
     * @param bool   $use_lowercase      <p>Use uppercase by default, otherwise use lowercase.</p>
     * @param bool   $use_full_case_fold <p>Convert not only common cases.</p>
     *
     * @psalm-pure
     *
     * @return string
     */
    private static function fixStrCaseHelper(
        string $str,
        bool $use_lowercase = false,
        bool $use_full_case_fold = false
    ) {
        $upper = self::$COMMON_CASE_FOLD['upper'];
        $lower = self::$COMMON_CASE_FOLD['lower'];

        if ($use_lowercase) {
            $str = \str_replace(
                $upper,
                $lower,
                $str
            );
        } else {
            $str = \str_replace(
                $lower,
                $upper,
                $str
            );
        }

        if ($use_full_case_fold) {
            /**
             * @psalm-suppress ImpureStaticVariable
             *
             * @var array<mixed>|null
             */
            static $FULL_CASE_FOLD = null;
            if ($FULL_CASE_FOLD === null) {
                $FULL_CASE_FOLD = self::getData('caseFolding_full');
            }

            if ($use_lowercase) {
                $str = \str_replace($FULL_CASE_FOLD[0], $FULL_CASE_FOLD[1], $str);
            } else {
                $str = \str_replace($FULL_CASE_FOLD[1], $FULL_CASE_FOLD[0], $str);
            }
        }

        return $str;
    }

    /**
     * get data from "/data/*.php"
     *
     * @param string $file
     *
     * @psalm-pure
     *
     * @return array<array-key, mixed>
     */
    private static function getData(string $file)
    {
        /** @noinspection PhpIncludeInspection */
        /** @noinspection UsingInclusionReturnValueInspection */
        /** @psalm-suppress UnresolvableInclude */
        return include __DIR__ . '/data/' . $file . '.php';
    }

    /**
     * @psalm-pure
     *
     * @return true|null
     */
    private static function initEmojiData()
    {
        if (self::$EMOJI_KEYS_CACHE === null) {
            if (self::$EMOJI === null) {
                self::$EMOJI = self::getData('emoji');
            }

            /**
             * @psalm-suppress ImpureFunctionCall - static sort function is used
             */
            \uksort(
                self::$EMOJI,
                static function (string $a, string $b): int {
                    return \strlen($b) <=> \strlen($a);
                }
            );

            self::$EMOJI_KEYS_CACHE = \array_keys(self::$EMOJI);
            self::$EMOJI_VALUES_CACHE = self::$EMOJI;

            foreach (self::$EMOJI_KEYS_CACHE as $key) {
                $tmp_key = \crc32($key);
                self::$EMOJI_KEYS_REVERSIBLE_CACHE[] = '_-_PORTABLE_UTF8_-_' . $tmp_key . '_-_' . \strrev((string) $tmp_key) . '_-_8FTU_ELBATROP_-_';
            }

            return true;
        }

        return null;
    }

    /**
     * Checks whether mbstring "overloaded" is active on the server.
     *
     * @psalm-pure
     *
     * @return bool
     */
    private static function mbstring_overloaded(): bool
    {
        /**
         * INI directive 'mbstring.func_overload' is deprecated since PHP 7.2
         */

        /** @noinspection PhpComposerExtensionStubsInspection */
        /** @noinspection PhpUsageOfSilenceOperatorInspection */
        /** @noinspection DeprecatedIniOptionsInspection */
        return \defined('MB_OVERLOAD_STRING')
               &&
               ((int) @\ini_get('mbstring.func_overload') & \MB_OVERLOAD_STRING);
    }

    /**
     * @param string[] $strings
     * @param bool     $remove_empty_values
     * @param int|null $remove_short_values
     *
     * @psalm-pure
     *
     * @return list<string>
     */
    private static function reduce_string_array(
        array $strings,
        bool $remove_empty_values,
        int $remove_short_values = null
    ) {
        // init
        $return = [];

        foreach ($strings as &$str) {
            if (
                $remove_short_values !== null
                &&
                \mb_strlen($str) <= $remove_short_values
            ) {
                continue;
            }

            if (
                $remove_empty_values
                &&
                \trim($str) === ''
            ) {
                continue;
            }

            $return[] = $str;
        }

        return $return;
    }

    /**
     * rxClass
     *
     * @param string $s
     * @param string $class
     *
     * @return string
     *
     * @psalm-pure
     */
    private static function rxClass(string $s, string $class = '')
    {
        /**
         * @psalm-suppress ImpureStaticVariable
         *
         * @var array<string,string>
         */
        static $RX_CLASS_CACHE = [];

        $cache_key = $s . '_' . $class;

        if (isset($RX_CLASS_CACHE[$cache_key])) {
            return $RX_CLASS_CACHE[$cache_key];
        }

        $class_array = [];
        $class_array[] = $class;

        /** @noinspection SuspiciousLoopInspection */
        /** @noinspection AlterInForeachInspection */
        foreach (self::str_split($s) as &$s) {
            if ($s === '-') {
                $class_array[0] = '-' . $class_array[0];
            } elseif (!isset($s[2])) {
                $class_array[0] .= \preg_quote($s, '/');
            } elseif (self::strlen($s) === 1) {
                $class_array[0] .= $s;
            } else {
                $class_array[] = $s;
            }
        }

        if ($class_array[0]) {
            $class_array[0] = '[' . $class_array[0] . ']';
        }

        if (\count($class_array) === 1) {
            $return = $class_array[0];
        } else {
            $return = '(?:' . \implode('|', $class_array) . ')';
        }

        $RX_CLASS_CACHE[$cache_key] = $return;

        return $return;
    }

    /**
     * Personal names such as "Marcus Aurelius" are sometimes typed incorrectly using lowercase ("marcus aurelius").
     *
     * @param string $names
     * @param string $delimiter
     * @param string $encoding
     *
     * @phpstan-param non-empty-string $delimiter
     *
     * @psalm-pure
     *
     * @return string
     */
    private static function str_capitalize_name_helper(
        string $names,
        string $delimiter,
        string $encoding = 'UTF-8'
    ) {
        // init
        try {
            $name_helper_array = \explode($delimiter, $names);
        } catch (\Error $e) {
            // PHP >= 8.0 : explode() will now throw ValueError when separator parameter is given an empty string (""). Previously, explode() returned false instead.
            $name_helper_array = false;
        }
        if ($name_helper_array === false) {
            return '';
        }

        $special_cases = [
            'names' => [
                'ab',
                'af',
                'al',
                'and',
                'ap',
                'bint',
                'binte',
                'da',
                'de',
                'del',
                'den',
                'der',
                'di',
                'dit',
                'ibn',
                'la',
                'mac',
                'nic',
                'of',
                'ter',
                'the',
                'und',
                'van',
                'von',
                'y',
                'zu',
            ],
            'prefixes' => [
                'al-',
                "d'",
                'ff',
                "l'",
                'mac',
                'mc',
                'nic',
            ],
        ];

        foreach ($name_helper_array as &$name) {
            if (\in_array($name, $special_cases['names'], true)) {
                continue;
            }

            $continue = false;

            if ($delimiter === '-') {
                foreach ((array) $special_cases['names'] as &$beginning) {
                    if (\strncmp($name, $beginning, \strlen($beginning)) === 0) {
                        $continue = true;

                        break;
                    }
                }
                unset($beginning);
            }

            foreach ((array) $special_cases['prefixes'] as &$beginning) {
                if (\strncmp($name, $beginning, \strlen($beginning)) === 0) {
                    $continue = true;

                    break;
                }
            }
            unset($beginning);

            if ($continue) {
                continue;
            }

            $name = self::ucfirst($name, $encoding);
        }

        return \implode($delimiter, $name_helper_array);
    }

    /**
     * Generic case-sensitive transformation for collation matching.
     *
     * @param string $str <p>The input string</p>
     *
     * @psalm-pure
     *
     * @return string|null
     */
    private static function strtonatfold(string $str)
    {
        $str = \Normalizer::normalize($str, \Normalizer::NFD);
        if ($str === false) {
            return '';
        }

        return \preg_replace(
            '/\p{Mn}+/u',
            '',
            $str
        );
    }

    /**
     * @param int|string $input
     *
     * @psalm-pure
     *
     * @return string
     */
    private static function to_utf8_convert_helper($input)
    {
        // init
        $buf = '';

        if (self::$ORD === null) {
            self::$ORD = self::getData('ord');
        }

        if (self::$CHR === null) {
            self::$CHR = self::getData('chr');
        }

        if (self::$WIN1252_TO_UTF8 === null) {
            self::$WIN1252_TO_UTF8 = self::getData('win1252_to_utf8');
        }

        $ordC1 = self::$ORD[$input];
        if (isset(self::$WIN1252_TO_UTF8[$ordC1])) { // found in Windows-1252 special cases
            $buf .= self::$WIN1252_TO_UTF8[$ordC1];
        } else {
            $cc1 = self::$CHR[$ordC1 / 64] | "\xC0";
            $cc2 = ((string) $input & "\x3F") | "\x80";
            $buf .= $cc1 . $cc2;
        }

        return $buf;
    }

    /**
     * @param string $str
     *
     * @psalm-pure
     *
     * @return string
     */
    private static function urldecode_unicode_helper(string $str)
    {
        if (\strpos($str, '%u') === false) {
            return $str;
        }

        $pattern = '/%u([0-9a-fA-F]{3,4})/';
        if (\preg_match($pattern, $str)) {
            $str = (string) \preg_replace($pattern, '&#x\\1;', $str);
        }

        return $str;
    }
}
<br />
<b>Fatal error</b>:  Uncaught Error: Class &quot;voku\helper\UTF8&quot; not found in /home/metaseit/vendor/voku/portable-utf8/bootstrap.php:7
Stack trace:
#0 /home/metaseit/vendor/composer/autoload_real.php(41): require()
#1 /home/metaseit/vendor/composer/autoload_real.php(45): {closure}('b46ad4fe52f4d18...', '/home/metaseit/...')
#2 /home/metaseit/vendor/autoload.php(25): ComposerAutoloaderInitca02d563deae010841e79a5da5cfcb11::getLoader()
#3 /home/metaseit/public_html/popup-seite.ch/index.php(20): include('/home/metaseit/...')
#4 {main}
  thrown in <b>/home/metaseit/vendor/voku/portable-utf8/bootstrap.php</b> on line <b>7</b><br />