Unicode.php

<?php

namespace Drupal\Component\Utility;


/**
 * Provides Unicode-related conversions and operations.
 *
 * @ingroup utility
 */
class Unicode {
    
    /**
     * Matches Unicode characters that are word boundaries.
     *
     * Characters with the following General_category (gc) property values are used
     * as word boundaries. While this does not fully conform to the Word Boundaries
     * algorithm described in http://unicode.org/reports/tr29, as PCRE does not
     * contain the Word_Break property table, this simpler algorithm has to do.
     * - Cc, Cf, Cn, Co, Cs: Other.
     * - Pc, Pd, Pe, Pf, Pi, Po, Ps: Punctuation.
     * - Sc, Sk, Sm, So: Symbols.
     * - Zl, Zp, Zs: Separators.
     *
     * Non-boundary characters include the following General_category (gc) property
     * values:
     * - Ll, Lm, Lo, Lt, Lu: Letters.
     * - Mc, Me, Mn: Combining Marks.
     * - Nd, Nl, No: Numbers.
     *
     * Note that the PCRE property matcher is not used because we wanted to be
     * compatible with Unicode 5.2.0 regardless of the PCRE version used (and any
     * bugs in PCRE property tables).
     *
     * @see http://unicode.org/glossary
     */
    const PREG_CLASS_WORD_BOUNDARY = <<<'EOD'
\x{0}-\x{2F}\x{3A}-\x{40}\x{5B}-\x{60}\x{7B}-\x{A9}\x{AB}-\x{B1}\x{B4}
\x{B6}-\x{B8}\x{BB}\x{BF}\x{D7}\x{F7}\x{2C2}-\x{2C5}\x{2D2}-\x{2DF}
\x{2E5}-\x{2EB}\x{2ED}\x{2EF}-\x{2FF}\x{375}\x{37E}-\x{385}\x{387}\x{3F6}
\x{482}\x{55A}-\x{55F}\x{589}-\x{58A}\x{5BE}\x{5C0}\x{5C3}\x{5C6}
\x{5F3}-\x{60F}\x{61B}-\x{61F}\x{66A}-\x{66D}\x{6D4}\x{6DD}\x{6E9}
\x{6FD}-\x{6FE}\x{700}-\x{70F}\x{7F6}-\x{7F9}\x{830}-\x{83E}
\x{964}-\x{965}\x{970}\x{9F2}-\x{9F3}\x{9FA}-\x{9FB}\x{AF1}\x{B70}
\x{BF3}-\x{BFA}\x{C7F}\x{CF1}-\x{CF2}\x{D79}\x{DF4}\x{E3F}\x{E4F}
\x{E5A}-\x{E5B}\x{F01}-\x{F17}\x{F1A}-\x{F1F}\x{F34}\x{F36}\x{F38}
\x{F3A}-\x{F3D}\x{F85}\x{FBE}-\x{FC5}\x{FC7}-\x{FD8}\x{104A}-\x{104F}
\x{109E}-\x{109F}\x{10FB}\x{1360}-\x{1368}\x{1390}-\x{1399}\x{1400}
\x{166D}-\x{166E}\x{1680}\x{169B}-\x{169C}\x{16EB}-\x{16ED}
\x{1735}-\x{1736}\x{17B4}-\x{17B5}\x{17D4}-\x{17D6}\x{17D8}-\x{17DB}
\x{1800}-\x{180A}\x{180E}\x{1940}-\x{1945}\x{19DE}-\x{19FF}
\x{1A1E}-\x{1A1F}\x{1AA0}-\x{1AA6}\x{1AA8}-\x{1AAD}\x{1B5A}-\x{1B6A}
\x{1B74}-\x{1B7C}\x{1C3B}-\x{1C3F}\x{1C7E}-\x{1C7F}\x{1CD3}\x{1FBD}
\x{1FBF}-\x{1FC1}\x{1FCD}-\x{1FCF}\x{1FDD}-\x{1FDF}\x{1FED}-\x{1FEF}
\x{1FFD}-\x{206F}\x{207A}-\x{207E}\x{208A}-\x{208E}\x{20A0}-\x{20B8}
\x{2100}-\x{2101}\x{2103}-\x{2106}\x{2108}-\x{2109}\x{2114}
\x{2116}-\x{2118}\x{211E}-\x{2123}\x{2125}\x{2127}\x{2129}\x{212E}
\x{213A}-\x{213B}\x{2140}-\x{2144}\x{214A}-\x{214D}\x{214F}
\x{2190}-\x{244A}\x{249C}-\x{24E9}\x{2500}-\x{2775}\x{2794}-\x{2B59}
\x{2CE5}-\x{2CEA}\x{2CF9}-\x{2CFC}\x{2CFE}-\x{2CFF}\x{2E00}-\x{2E2E}
\x{2E30}-\x{3004}\x{3008}-\x{3020}\x{3030}\x{3036}-\x{3037}
\x{303D}-\x{303F}\x{309B}-\x{309C}\x{30A0}\x{30FB}\x{3190}-\x{3191}
\x{3196}-\x{319F}\x{31C0}-\x{31E3}\x{3200}-\x{321E}\x{322A}-\x{3250}
\x{3260}-\x{327F}\x{328A}-\x{32B0}\x{32C0}-\x{33FF}\x{4DC0}-\x{4DFF}
\x{A490}-\x{A4C6}\x{A4FE}-\x{A4FF}\x{A60D}-\x{A60F}\x{A673}\x{A67E}
\x{A6F2}-\x{A716}\x{A720}-\x{A721}\x{A789}-\x{A78A}\x{A828}-\x{A82B}
\x{A836}-\x{A839}\x{A874}-\x{A877}\x{A8CE}-\x{A8CF}\x{A8F8}-\x{A8FA}
\x{A92E}-\x{A92F}\x{A95F}\x{A9C1}-\x{A9CD}\x{A9DE}-\x{A9DF}
\x{AA5C}-\x{AA5F}\x{AA77}-\x{AA79}\x{AADE}-\x{AADF}\x{ABEB}
\x{E000}-\x{F8FF}\x{FB29}\x{FD3E}-\x{FD3F}\x{FDFC}-\x{FDFD}
\x{FE10}-\x{FE19}\x{FE30}-\x{FE6B}\x{FEFF}-\x{FF0F}\x{FF1A}-\x{FF20}
\x{FF3B}-\x{FF40}\x{FF5B}-\x{FF65}\x{FFE0}-\x{FFFD}
EOD;
    
    /**
     * Indicates that standard PHP (emulated) unicode support is being used.
     */
    const STATUS_SINGLEBYTE = 0;
    
    /**
     * Indicates that full unicode support with the PHP mbstring extension is
     * being used.
     */
    const STATUS_MULTIBYTE = 1;
    
    /**
     * Indicates an error during check for PHP unicode support.
     */
    const STATUS_ERROR = -1;
    
    /**
     * Gets the current status of unicode/multibyte support on this environment.
     *
     * @return int
     *   The status of multibyte support. It can be one of:
     *   - \Drupal\Component\Utility\Unicode::STATUS_MULTIBYTE
     *     Full unicode support using an extension.
     *   - \Drupal\Component\Utility\Unicode::STATUS_SINGLEBYTE
     *     Standard PHP (emulated) unicode support.
     *   - \Drupal\Component\Utility\Unicode::STATUS_ERROR
     *     An error occurred. No unicode support.
     */
    public static function getStatus() {
        switch (static::check()) {
            case 'mb_strlen':
                return Unicode::STATUS_SINGLEBYTE;
            case '':
                return Unicode::STATUS_MULTIBYTE;
        }
        return Unicode::STATUS_ERROR;
    }
    
    /**
     * Sets the value for multibyte support status for the current environment.
     *
     * The following status keys are supported:
     *   - \Drupal\Component\Utility\Unicode::STATUS_MULTIBYTE
     *     Full unicode support using an extension.
     *   - \Drupal\Component\Utility\Unicode::STATUS_SINGLEBYTE
     *     Standard PHP (emulated) unicode support.
     *   - \Drupal\Component\Utility\Unicode::STATUS_ERROR
     *     An error occurred. No unicode support.
     *
     * @param int $status
     *   The new status of multibyte support.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. In
     *   Drupal 9 there will be no way to set the status and in Drupal 8 this
     *   ability has been removed because mb_*() functions are supplied using
     *   Symfony's polyfill.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function setStatus($status) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::setStatus() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. In Drupal 9 there will be no way to set the status and in Drupal 8 this ability has been removed because mb_*() functions are supplied using Symfony\'s polyfill. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
    }
    
    /**
     * Checks for Unicode support in PHP and sets the proper settings if possible.
     *
     * Because of the need to be able to handle text in various encodings, we do
     * not support mbstring function overloading. HTTP input/output conversion
     * must be disabled for similar reasons.
     *
     * @return string
     *   A string identifier of a failed multibyte extension check, if any.
     *   Otherwise, an empty string.
     */
    public static function check() {
        // Set appropriate configuration.
        mb_internal_encoding('utf-8');
        mb_language('uni');
        // Check for mbstring extension.
        if (!extension_loaded('mbstring')) {
            return 'mb_strlen';
        }
        // Check mbstring configuration.
        if (ini_get('mbstring.func_overload') != 0) {
            return 'mbstring.func_overload';
        }
        if (ini_get('mbstring.encoding_translation') != 0) {
            return 'mbstring.encoding_translation';
        }
        return '';
    }
    
    /**
     * Decodes UTF byte-order mark (BOM) into the encoding's name.
     *
     * @param string $data
     *   The data possibly containing a BOM. This can be the entire contents of
     *   a file, or just a fragment containing at least the first five bytes.
     *
     * @return string|bool
     *   The name of the encoding, or FALSE if no byte order mark was present.
     */
    public static function encodingFromBOM($data) {
        static $bomMap = [
            "" => 'UTF-8',
            "\xfe\xff" => 'UTF-16BE',
            "\xff\xfe" => 'UTF-16LE',
            "\x00\x00\xfe\xff" => 'UTF-32BE',
            "\xff\xfe\x00\x00" => 'UTF-32LE',
            "+/v8" => 'UTF-7',
            "+/v9" => 'UTF-7',
            "+/v+" => 'UTF-7',
            "+/v/" => 'UTF-7',
            "+/v8-" => 'UTF-7',
        ];
        foreach ($bomMap as $bom => $encoding) {
            if (strpos($data, $bom) === 0) {
                return $encoding;
            }
        }
        return FALSE;
    }
    
    /**
     * Converts data to UTF-8.
     *
     * Requires the iconv, GNU recode or mbstring PHP extension.
     *
     * @param string $data
     *   The data to be converted.
     * @param string $encoding
     *   The encoding that the data is in.
     *
     * @return string|bool
     *   Converted data or FALSE.
     */
    public static function convertToUtf8($data, $encoding) {
        return @iconv($encoding, 'utf-8', $data);
    }
    
    /**
     * Truncates a UTF-8-encoded string safely to a number of bytes.
     *
     * If the end position is in the middle of a UTF-8 sequence, it scans backwards
     * until the beginning of the byte sequence.
     *
     * Use this function whenever you want to chop off a string at an unsure
     * location. On the other hand, if you're sure that you're splitting on a
     * character boundary (e.g. after using strpos() or similar), you can safely
     * use substr() instead.
     *
     * @param string $string
     *   The string to truncate.
     * @param int $len
     *   An upper limit on the returned string length.
     *
     * @return string
     *   The truncated string.
     */
    public static function truncateBytes($string, $len) {
        if (strlen($string) <= $len) {
            return $string;
        }
        if (ord($string[$len]) < 0x80 || ord($string[$len]) >= 0xc0) {
            return substr($string, 0, $len);
        }
        // Scan backwards to beginning of the byte sequence.
        // @todo Make the code more readable in https://www.drupal.org/node/2911497.
        while (--$len >= 0 && ord($string[$len]) >= 0x80 && ord($string[$len]) < 0xc0) {
        }
        return substr($string, 0, $len);
    }
    
    /**
     * Counts the number of characters in a UTF-8 string.
     *
     * This is less than or equal to the byte count.
     *
     * @param string $text
     *   The string to run the operation on.
     *
     * @return int
     *   The length of the string.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. Use
     *   mb_strlen() instead.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function strlen($text) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::strlen() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. Use mb_strlen() instead. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
        return mb_strlen($text);
    }
    
    /**
     * Converts a UTF-8 string to uppercase.
     *
     * @param string $text
     *   The string to run the operation on.
     *
     * @return string
     *   The string in uppercase.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. Use
     *   mb_strtoupper() instead.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function strtoupper($text) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::strtoupper() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. Use mb_strtoupper() instead. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
        return mb_strtoupper($text);
    }
    
    /**
     * Converts a UTF-8 string to lowercase.
     *
     * @param string $text
     *   The string to run the operation on.
     *
     * @return string
     *   The string in lowercase.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. Use
     *   mb_strtolower() instead.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function strtolower($text) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::strtolower() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. Use mb_strtolower() instead. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
        return mb_strtolower($text);
    }
    
    /**
     * Capitalizes the first character of a UTF-8 string.
     *
     * @param string $text
     *   The string to convert.
     *
     * @return string
     *   The string with the first character as uppercase.
     */
    public static function ucfirst($text) {
        return mb_strtoupper(mb_substr($text, 0, 1)) . mb_substr($text, 1);
    }
    
    /**
     * Converts the first character of a UTF-8 string to lowercase.
     *
     * @param string $text
     *   The string that will be converted.
     *
     * @return string
     *   The string with the first character as lowercase.
     *
     * @ingroup php_wrappers
     */
    public static function lcfirst($text) {
        // Note: no mbstring equivalent!
        return mb_strtolower(mb_substr($text, 0, 1)) . mb_substr($text, 1);
    }
    
    /**
     * Capitalizes the first character of each word in a UTF-8 string.
     *
     * @param string $text
     *   The text that will be converted.
     *
     * @return string
     *   The input $text with each word capitalized.
     *
     * @ingroup php_wrappers
     */
    public static function ucwords($text) {
        $regex = '/(^|[' . static::PREG_CLASS_WORD_BOUNDARY . '])([^' . static::PREG_CLASS_WORD_BOUNDARY . '])/u';
        return preg_replace_callback($regex, function (array $matches) {
            return $matches[1] . mb_strtoupper($matches[2]);
        }, $text);
    }
    
    /**
     * Cuts off a piece of a string based on character indices and counts.
     *
     * Follows the same behavior as PHP's own substr() function. Note that for
     * cutting off a string at a known character/substring location, the usage of
     * PHP's normal strpos/substr is safe and much faster.
     *
     * @param string $text
     *   The input string.
     * @param int $start
     *   The position at which to start reading.
     * @param int $length
     *   The number of characters to read.
     *
     * @return string
     *   The shortened string.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. Use
     *   mb_substr() instead.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function substr($text, $start, $length = NULL) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::substr() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. Use mb_substr() instead. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
        return mb_substr($text, $start, $length);
    }
    
    /**
     * Truncates a UTF-8-encoded string safely to a number of characters.
     *
     * @param string $string
     *   The string to truncate.
     * @param int $max_length
     *   An upper limit on the returned string length, including trailing ellipsis
     *   if $add_ellipsis is TRUE.
     * @param bool $wordsafe
     *   If TRUE, attempt to truncate on a word boundary. Word boundaries are
     *   spaces, punctuation, and Unicode characters used as word boundaries in
     *   non-Latin languages; see Unicode::PREG_CLASS_WORD_BOUNDARY for more
     *   information. If a word boundary cannot be found that would make the length
     *   of the returned string fall within length guidelines (see parameters
     *   $max_length and $min_wordsafe_length), word boundaries are ignored.
     * @param bool $add_ellipsis
     *   If TRUE, add '...' to the end of the truncated string (defaults to
     *   FALSE). The string length will still fall within $max_length.
     * @param int $min_wordsafe_length
     *   If $wordsafe is TRUE, the minimum acceptable length for truncation (before
     *   adding an ellipsis, if $add_ellipsis is TRUE). Has no effect if $wordsafe
     *   is FALSE. This can be used to prevent having a very short resulting string
     *   that will not be understandable. For instance, if you are truncating the
     *   string "See myverylongurlexample.com for more information" to a word-safe
     *   return length of 20, the only available word boundary within 20 characters
     *   is after the word "See", which wouldn't leave a very informative string. If
     *   you had set $min_wordsafe_length to 10, though, the function would realise
     *   that "See" alone is too short, and would then just truncate ignoring word
     *   boundaries, giving you "See myverylongurl..." (assuming you had set
     *   $add_ellipses to TRUE).
     *
     * @return string
     *   The truncated string.
     */
    public static function truncate($string, $max_length, $wordsafe = FALSE, $add_ellipsis = FALSE, $min_wordsafe_length = 1) {
        $ellipsis = '';
        $max_length = max($max_length, 0);
        $min_wordsafe_length = max($min_wordsafe_length, 0);
        if (mb_strlen($string) <= $max_length) {
            // No truncation needed, so don't add ellipsis, just return.
            return $string;
        }
        if ($add_ellipsis) {
            // Truncate ellipsis in case $max_length is small.
            $ellipsis = mb_substr('…', 0, $max_length);
            $max_length -= mb_strlen($ellipsis);
            $max_length = max($max_length, 0);
        }
        if ($max_length <= $min_wordsafe_length) {
            // Do not attempt word-safe if lengths are bad.
            $wordsafe = FALSE;
        }
        if ($wordsafe) {
            $matches = [];
            // Find the last word boundary, if there is one within $min_wordsafe_length
            // to $max_length characters. preg_match() is always greedy, so it will
            // find the longest string possible.
            $found = preg_match('/^(.{' . $min_wordsafe_length . ',' . $max_length . '})[' . Unicode::PREG_CLASS_WORD_BOUNDARY . ']/us', $string, $matches);
            if ($found) {
                $string = $matches[1];
            }
            else {
                $string = mb_substr($string, 0, $max_length);
            }
        }
        else {
            $string = mb_substr($string, 0, $max_length);
        }
        if ($add_ellipsis) {
            // If we're adding an ellipsis, remove any trailing periods.
            $string = rtrim($string, '.');
            $string .= $ellipsis;
        }
        return $string;
    }
    
    /**
     * Compares UTF-8-encoded strings in a binary safe case-insensitive manner.
     *
     * @param string $str1
     *   The first string.
     * @param string $str2
     *   The second string.
     *
     * @return int
     *   Returns < 0 if $str1 is less than $str2; > 0 if $str1 is greater than
     *   $str2, and 0 if they are equal.
     */
    public static function strcasecmp($str1, $str2) {
        return strcmp(mb_strtoupper($str1), mb_strtoupper($str2));
    }
    
    /**
     * Encodes MIME/HTTP headers that contain incorrectly encoded characters.
     *
     * For example, Unicode::mimeHeaderEncode('tést.txt') returns
     * "=?UTF-8?B?dMOpc3QudHh0?=".
     *
     * See http://www.rfc-editor.org/rfc/rfc2047.txt for more information.
     *
     * Notes:
     * - Only encode strings that contain non-ASCII characters.
     * - We progressively cut-off a chunk with self::truncateBytes(). This ensures
     *   each chunk starts and ends on a character boundary.
     * - Using \n as the chunk separator may cause problems on some systems and
     *   may have to be changed to \r\n or \r.
     *
     * @param string $string
     *   The header to encode.
     * @param bool $shorten
     *   If TRUE, only return the first chunk of a multi-chunk encoded string.
     *
     * @return string
     *   The mime-encoded header.
     */
    public static function mimeHeaderEncode($string, $shorten = FALSE) {
        if (preg_match('/[^\\x20-\\x7E]/', $string)) {
            // floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
            $chunk_size = 47;
            $len = strlen($string);
            $output = '';
            while ($len > 0) {
                $chunk = static::truncateBytes($string, $chunk_size);
                $output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\n";
                if ($shorten) {
                    break;
                }
                $c = strlen($chunk);
                $string = substr($string, $c);
                $len -= $c;
            }
            return trim($output);
        }
        return $string;
    }
    
    /**
     * Decodes MIME/HTTP encoded header values.
     *
     * @param string $header
     *   The header to decode.
     *
     * @return string
     *   The mime-decoded header.
     */
    public static function mimeHeaderDecode($header) {
        $callback = function ($matches) {
            $data = strtolower($matches[2]) == 'b' ? base64_decode($matches[3]) : str_replace('_', ' ', quoted_printable_decode($matches[3]));
            if (strtolower($matches[1]) != 'utf-8') {
                $data = static::convertToUtf8($data, $matches[1]);
            }
            return $data;
        };
        // First step: encoded chunks followed by other encoded chunks (need to collapse whitespace)
        $header = preg_replace_callback('/=\\?([^?]+)\\?([Qq]|[Bb])\\?([^?]+|\\?(?!=))\\?=\\s+(?==\\?)/', $callback, $header);
        // Second step: remaining chunks (do not collapse whitespace)
        return preg_replace_callback('/=\\?([^?]+)\\?([Qq]|[Bb])\\?([^?]+|\\?(?!=))\\?=/', $callback, $header);
    }
    
    /**
     * Flip U+C0-U+DE to U+E0-U+FD and back. Can be used as preg_replace callback.
     *
     * @param array $matches
     *   An array of matches by preg_replace_callback().
     *
     * @return string
     *   The flipped text.
     *
     * @deprecated in drupal:8.8.0 and is removed from drupal:9.0.0. There is
     *   no direct replacement.
     *
     * @see https://www.drupal.org/node/3057322
     */
    public static function caseFlip($matches) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::caseFlip() is deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. There is no direct replacement. See https://www.drupal.org/node/3057322', E_USER_DEPRECATED);
        return $matches[0][0] . chr(ord($matches[0][1]) ^ 32);
    }
    
    /**
     * Checks whether a string is valid UTF-8.
     *
     * All functions designed to filter input should use drupal_validate_utf8
     * to ensure they operate on valid UTF-8 strings to prevent bypass of the
     * filter.
     *
     * When text containing an invalid UTF-8 lead byte (0xC0 - 0xFF) is presented
     * as UTF-8 to Internet Explorer 6, the program may misinterpret subsequent
     * bytes. When these subsequent bytes are HTML control characters such as
     * quotes or angle brackets, parts of the text that were deemed safe by filters
     * end up in locations that are potentially unsafe; An onerror attribute that
     * is outside of a tag, and thus deemed safe by a filter, can be interpreted
     * by the browser as if it were inside the tag.
     *
     * The function does not return FALSE for strings containing character codes
     * above U+10FFFF, even though these are prohibited by RFC 3629.
     *
     * @param string $text
     *   The text to check.
     *
     * @return bool
     *   TRUE if the text is valid UTF-8, FALSE if not.
     */
    public static function validateUtf8($text) {
        if (strlen($text) == 0) {
            return TRUE;
        }
        // With the PCRE_UTF8 modifier 'u', preg_match() fails silently on strings
        // containing invalid UTF-8 byte sequences. It does not reject character
        // codes above U+10FFFF (represented by 4 or more octets), though.
        return preg_match('/^./us', $text) == 1;
    }
    
    /**
     * Finds the position of the first occurrence of a string in another string.
     *
     * @param string $haystack
     *   The string to search in.
     * @param string $needle
     *   The string to find in $haystack.
     * @param int $offset
     *   If specified, start the search at this number of characters from the
     *   beginning (default 0).
     *
     * @return int|false
     *   The position where $needle occurs in $haystack, always relative to the
     *   beginning (independent of $offset), or FALSE if not found. Note that
     *   a return value of 0 is not the same as FALSE.
     *
     * @deprecated in drupal:8.6.0 and is removed from drupal:9.0.0. Use
     *   mb_strpos() instead.
     *
     * @see https://www.drupal.org/node/2850048
     */
    public static function strpos($haystack, $needle, $offset = 0) {
        @trigger_error('\\Drupal\\Component\\Utility\\Unicode::strpos() is deprecated in Drupal 8.6.0 and will be removed before Drupal 9.0.0. Use mb_strpos() instead. See https://www.drupal.org/node/2850048.', E_USER_DEPRECATED);
        return mb_strpos($haystack, $needle, $offset);
    }

}