diff --git a/Mbstring.php b/Mbstring.php
index 1fc4fee..693749f 100644
--- a/Mbstring.php
+++ b/Mbstring.php
@@ -67,19 +67,20 @@
  */
 final class Mbstring
 {
-    const MB_CASE_FOLD = PHP_INT_MAX;
+    public const MB_CASE_FOLD = \PHP_INT_MAX;
 
-    private static $encodingList = array('ASCII', 'UTF-8');
+    private const CASE_FOLD = [
+        ['µ', 'ſ', "\xCD\x85", 'ς', "\xCF\x90", "\xCF\x91", "\xCF\x95", "\xCF\x96", "\xCF\xB0", "\xCF\xB1", "\xCF\xB5", "\xE1\xBA\x9B", "\xE1\xBE\xBE"],
+        ['μ', 's', 'ι',        'σ', 'β',        'θ',        'φ',        'π',        'κ',        'ρ',        'ε',        "\xE1\xB9\xA1", 'ι'],
+    ];
+
+    private static $encodingList = ['ASCII', 'UTF-8'];
     private static $language = 'neutral';
     private static $internalEncoding = 'UTF-8';
-    private static $caseFold = array(
-        array('µ', 'ſ', "\xCD\x85", 'ς', "\xCF\x90", "\xCF\x91", "\xCF\x95", "\xCF\x96", "\xCF\xB0", "\xCF\xB1", "\xCF\xB5", "\xE1\xBA\x9B", "\xE1\xBE\xBE"),
-        array('μ', 's', 'ι',        'σ', 'β',        'θ',        'φ',        'π',        'κ',        'ρ',        'ε',        "\xE1\xB9\xA1", 'ι'),
-    );
 
     public static function mb_convert_encoding($s, $toEncoding, $fromEncoding = null)
     {
-        if (\is_array($fromEncoding) || false !== strpos($fromEncoding, ',')) {
+        if (\is_array($fromEncoding) || ($fromEncoding !== null && false !== strpos($fromEncoding, ','))) {
             $fromEncoding = self::mb_detect_encoding($s, $fromEncoding);
         } else {
             $fromEncoding = self::getEncoding($fromEncoding);
@@ -101,27 +102,25 @@ public static function mb_convert_encoding($s, $toEncoding, $fromEncoding = null
                 $fromEncoding = 'Windows-1252';
             }
             if ('UTF-8' !== $fromEncoding) {
-                $s = iconv($fromEncoding, 'UTF-8//IGNORE', $s);
+                $s = \iconv($fromEncoding, 'UTF-8//IGNORE', $s);
             }
 
-            return preg_replace_callback('/[\x80-\xFF]+/', array(__CLASS__, 'html_encoding_callback'), $s);
+            return preg_replace_callback('/[\x80-\xFF]+/', [__CLASS__, 'html_encoding_callback'], $s);
         }
 
         if ('HTML-ENTITIES' === $fromEncoding) {
-            $s = html_entity_decode($s, ENT_COMPAT, 'UTF-8');
+            $s = html_entity_decode($s, \ENT_COMPAT, 'UTF-8');
             $fromEncoding = 'UTF-8';
         }
 
-        return iconv($fromEncoding, $toEncoding.'//IGNORE', $s);
+        return \iconv($fromEncoding, $toEncoding.'//IGNORE', $s);
     }
 
-    public static function mb_convert_variables($toEncoding, $fromEncoding, &$a = null, &$b = null, &$c = null, &$d = null, &$e = null, &$f = null)
+    public static function mb_convert_variables($toEncoding, $fromEncoding, &...$vars)
     {
-        $vars = array(&$a, &$b, &$c, &$d, &$e, &$f);
-
         $ok = true;
         array_walk_recursive($vars, function (&$v) use (&$ok, $toEncoding, $fromEncoding) {
-            if (false === $v = Mbstring::mb_convert_encoding($v, $toEncoding, $fromEncoding)) {
+            if (false === $v = self::mb_convert_encoding($v, $toEncoding, $fromEncoding)) {
                 $ok = false;
             }
         });
@@ -131,28 +130,28 @@ public static function mb_convert_variables($toEncoding, $fromEncoding, &$a = nu
 
     public static function mb_decode_mimeheader($s)
     {
-        return iconv_mime_decode($s, 2, self::$internalEncoding);
+        return \iconv_mime_decode($s, 2, self::$internalEncoding);
     }
 
     public static function mb_encode_mimeheader($s, $charset = null, $transferEncoding = null, $linefeed = null, $indent = null)
     {
-        trigger_error('mb_encode_mimeheader() is bugged. Please use iconv_mime_encode() instead', E_USER_WARNING);
+        trigger_error('mb_encode_mimeheader() is bugged. Please use iconv_mime_encode() instead', \E_USER_WARNING);
     }
 
     public static function mb_decode_numericentity($s, $convmap, $encoding = null)
     {
-        if (null !== $s && !\is_scalar($s) && !(\is_object($s) && \method_exists($s, '__toString'))) {
-            trigger_error('mb_decode_numericentity() expects parameter 1 to be string, '.\gettype($s).' given', E_USER_WARNING);
+        if (null !== $s && !is_scalar($s) && !(\is_object($s) && method_exists($s, '__toString'))) {
+            trigger_error('mb_decode_numericentity() expects parameter 1 to be string, '.\gettype($s).' given', \E_USER_WARNING);
 
             return null;
         }
 
-        if (!\is_array($convmap) || !$convmap) {
+        if (!\is_array($convmap) || (80000 > \PHP_VERSION_ID && !$convmap)) {
             return false;
         }
 
-        if (null !== $encoding && !\is_scalar($encoding)) {
-            trigger_error('mb_decode_numericentity() expects parameter 3 to be string, '.\gettype($s).' given', E_USER_WARNING);
+        if (null !== $encoding && !is_scalar($encoding)) {
+            trigger_error('mb_decode_numericentity() expects parameter 3 to be string, '.\gettype($s).' given', \E_USER_WARNING);
 
             return '';  // Instead of null (cf. mb_encode_numericentity).
         }
@@ -167,10 +166,10 @@ public static function mb_decode_numericentity($s, $convmap, $encoding = null)
         if ('UTF-8' === $encoding) {
             $encoding = null;
             if (!preg_match('//u', $s)) {
-                $s = @iconv('UTF-8', 'UTF-8//IGNORE', $s);
+                $s = @\iconv('UTF-8', 'UTF-8//IGNORE', $s);
             }
         } else {
-            $s = iconv($encoding, 'UTF-8//IGNORE', $s);
+            $s = \iconv($encoding, 'UTF-8//IGNORE', $s);
         }
 
         $cnt = floor(\count($convmap) / 4) * 4;
@@ -185,7 +184,7 @@ public static function mb_decode_numericentity($s, $convmap, $encoding = null)
             $c = isset($m[2]) ? (int) hexdec($m[2]) : $m[1];
             for ($i = 0; $i < $cnt; $i += 4) {
                 if ($c >= $convmap[$i] && $c <= $convmap[$i + 1]) {
-                    return Mbstring::mb_chr($c - $convmap[$i + 2]);
+                    return self::mb_chr($c - $convmap[$i + 2]);
                 }
             }
 
@@ -196,29 +195,29 @@ public static function mb_decode_numericentity($s, $convmap, $encoding = null)
             return $s;
         }
 
-        return iconv('UTF-8', $encoding.'//IGNORE', $s);
+        return \iconv('UTF-8', $encoding.'//IGNORE', $s);
     }
 
     public static function mb_encode_numericentity($s, $convmap, $encoding = null, $is_hex = false)
     {
-        if (null !== $s && !\is_scalar($s) && !(\is_object($s) && \method_exists($s, '__toString'))) {
-            trigger_error('mb_encode_numericentity() expects parameter 1 to be string, '.\gettype($s).' given', E_USER_WARNING);
+        if (null !== $s && !is_scalar($s) && !(\is_object($s) && method_exists($s, '__toString'))) {
+            trigger_error('mb_encode_numericentity() expects parameter 1 to be string, '.\gettype($s).' given', \E_USER_WARNING);
 
             return null;
         }
 
-        if (!\is_array($convmap) || !$convmap) {
+        if (!\is_array($convmap) || (80000 > \PHP_VERSION_ID && !$convmap)) {
             return false;
         }
 
-        if (null !== $encoding && !\is_scalar($encoding)) {
-            trigger_error('mb_encode_numericentity() expects parameter 3 to be string, '.\gettype($s).' given', E_USER_WARNING);
+        if (null !== $encoding && !is_scalar($encoding)) {
+            trigger_error('mb_encode_numericentity() expects parameter 3 to be string, '.\gettype($s).' given', \E_USER_WARNING);
 
             return null;  // Instead of '' (cf. mb_decode_numericentity).
         }
 
-        if (null !== $is_hex && !\is_scalar($is_hex)) {
-            trigger_error('mb_encode_numericentity() expects parameter 4 to be boolean, '.\gettype($s).' given', E_USER_WARNING);
+        if (null !== $is_hex && !is_scalar($is_hex)) {
+            trigger_error('mb_encode_numericentity() expects parameter 4 to be boolean, '.\gettype($s).' given', \E_USER_WARNING);
 
             return null;
         }
@@ -233,13 +232,13 @@ public static function mb_encode_numericentity($s, $convmap, $encoding = null, $
         if ('UTF-8' === $encoding) {
             $encoding = null;
             if (!preg_match('//u', $s)) {
-                $s = @iconv('UTF-8', 'UTF-8//IGNORE', $s);
+                $s = @\iconv('UTF-8', 'UTF-8//IGNORE', $s);
             }
         } else {
-            $s = iconv($encoding, 'UTF-8//IGNORE', $s);
+            $s = \iconv($encoding, 'UTF-8//IGNORE', $s);
         }
 
-        static $ulenMask = array("\xC0" => 2, "\xD0" => 2, "\xE0" => 3, "\xF0" => 4);
+        static $ulenMask = ["\xC0" => 2, "\xD0" => 2, "\xE0" => 3, "\xF0" => 4];
 
         $cnt = floor(\count($convmap) / 4) * 4;
         $i = 0;
@@ -266,7 +265,7 @@ public static function mb_encode_numericentity($s, $convmap, $encoding = null, $
             return $result;
         }
 
-        return iconv('UTF-8', $encoding.'//IGNORE', $result);
+        return \iconv('UTF-8', $encoding.'//IGNORE', $result);
     }
 
     public static function mb_convert_case($s, $mode, $encoding = null)
@@ -281,20 +280,20 @@ public static function mb_convert_case($s, $mode, $encoding = null)
         if ('UTF-8' === $encoding) {
             $encoding = null;
             if (!preg_match('//u', $s)) {
-                $s = @iconv('UTF-8', 'UTF-8//IGNORE', $s);
+                $s = @\iconv('UTF-8', 'UTF-8//IGNORE', $s);
             }
         } else {
-            $s = iconv($encoding, 'UTF-8//IGNORE', $s);
+            $s = \iconv($encoding, 'UTF-8//IGNORE', $s);
         }
 
-        if (MB_CASE_TITLE == $mode) {
+        if (\MB_CASE_TITLE == $mode) {
             static $titleRegexp = null;
             if (null === $titleRegexp) {
                 $titleRegexp = self::getData('titleCaseRegexp');
             }
-            $s = preg_replace_callback($titleRegexp, array(__CLASS__, 'title_case'), $s);
+            $s = preg_replace_callback($titleRegexp, [__CLASS__, 'title_case'], $s);
         } else {
-            if (MB_CASE_UPPER == $mode) {
+            if (\MB_CASE_UPPER == $mode) {
                 static $upper = null;
                 if (null === $upper) {
                     $upper = self::getData('upperCase');
@@ -302,7 +301,7 @@ public static function mb_convert_case($s, $mode, $encoding = null)
                 $map = $upper;
             } else {
                 if (self::MB_CASE_FOLD === $mode) {
-                    $s = str_replace(self::$caseFold[0], self::$caseFold[1], $s);
+                    $s = str_replace(self::CASE_FOLD[0], self::CASE_FOLD[1], $s);
                 }
 
                 static $lower = null;
@@ -312,7 +311,7 @@ public static function mb_convert_case($s, $mode, $encoding = null)
                 $map = $lower;
             }
 
-            static $ulenMask = array("\xC0" => 2, "\xD0" => 2, "\xE0" => 3, "\xF0" => 4);
+            static $ulenMask = ["\xC0" => 2, "\xD0" => 2, "\xE0" => 3, "\xF0" => 4];
 
             $i = 0;
             $len = \strlen($s);
@@ -344,7 +343,7 @@ public static function mb_convert_case($s, $mode, $encoding = null)
             return $s;
         }
 
-        return iconv('UTF-8', $encoding.'//IGNORE', $s);
+        return \iconv('UTF-8', $encoding.'//IGNORE', $s);
     }
 
     public static function mb_internal_encoding($encoding = null)
@@ -353,15 +352,19 @@ public static function mb_internal_encoding($encoding = null)
             return self::$internalEncoding;
         }
 
-        $encoding = self::getEncoding($encoding);
+        $normalizedEncoding = self::getEncoding($encoding);
 
-        if ('UTF-8' === $encoding || false !== @iconv($encoding, $encoding, ' ')) {
-            self::$internalEncoding = $encoding;
+        if ('UTF-8' === $normalizedEncoding || false !== @\iconv($normalizedEncoding, $normalizedEncoding, ' ')) {
+            self::$internalEncoding = $normalizedEncoding;
 
             return true;
         }
 
-        return false;
+        if (80000 > \PHP_VERSION_ID) {
+            return false;
+        }
+
+        throw new \ValueError(sprintf('Argument #1 ($encoding) must be a valid encoding, "%s" given', $encoding));
     }
 
     public static function mb_language($lang = null)
@@ -370,20 +373,24 @@ public static function mb_language($lang = null)
             return self::$language;
         }
 
-        switch ($lang = strtolower($lang)) {
+        switch ($normalizedLang = strtolower($lang)) {
             case 'uni':
             case 'neutral':
-                self::$language = $lang;
+                self::$language = $normalizedLang;
 
                 return true;
         }
 
-        return false;
+        if (80000 > \PHP_VERSION_ID) {
+            return false;
+        }
+
+        throw new \ValueError(sprintf('Argument #1 ($language) must be a valid language, "%s" given', $lang));
     }
 
     public static function mb_list_encodings()
     {
-        return array('UTF-8');
+        return ['UTF-8'];
     }
 
     public static function mb_encoding_aliases($encoding)
@@ -391,7 +398,7 @@ public static function mb_encoding_aliases($encoding)
         switch (strtoupper($encoding)) {
             case 'UTF8':
             case 'UTF-8':
-                return array('utf8');
+                return ['utf8'];
         }
 
         return false;
@@ -406,7 +413,7 @@ public static function mb_check_encoding($var = null, $encoding = null)
             $encoding = self::$internalEncoding;
         }
 
-        return self::mb_detect_encoding($var, array($encoding)) || false !== @iconv($encoding, $encoding, $var);
+        return self::mb_detect_encoding($var, [$encoding]) || false !== @\iconv($encoding, $encoding, $var);
     }
 
     public static function mb_detect_encoding($str, $encodingList = null, $strict = false)
@@ -481,7 +488,7 @@ public static function mb_strlen($s, $encoding = null)
             return \strlen($s);
         }
 
-        return @iconv_strlen($s, $encoding);
+        return @\iconv_strlen($s, $encoding);
     }
 
     public static function mb_strpos($haystack, $needle, $offset = 0, $encoding = null)
@@ -493,12 +500,16 @@ public static function mb_strpos($haystack, $needle, $offset = 0, $encoding = nu
 
         $needle = (string) $needle;
         if ('' === $needle) {
-            trigger_error(__METHOD__.': Empty delimiter', E_USER_WARNING);
+            if (80000 > \PHP_VERSION_ID) {
+                trigger_error(__METHOD__.': Empty delimiter', \E_USER_WARNING);
 
-            return false;
+                return false;
+            }
+
+            return 0;
         }
 
-        return iconv_strpos($haystack, $needle, $offset, $encoding);
+        return \iconv_strpos($haystack, $needle, $offset, $encoding);
     }
 
     public static function mb_strrpos($haystack, $needle, $offset = 0, $encoding = null)
@@ -512,37 +523,55 @@ public static function mb_strrpos($haystack, $needle, $offset = 0, $encoding = n
             $offset = 0;
         } elseif ($offset = (int) $offset) {
             if ($offset < 0) {
-                $haystack = self::mb_substr($haystack, 0, $offset, $encoding);
+                if (0 > $offset += self::mb_strlen($needle)) {
+                    $haystack = self::mb_substr($haystack, 0, $offset, $encoding);
+                }
                 $offset = 0;
             } else {
                 $haystack = self::mb_substr($haystack, $offset, 2147483647, $encoding);
             }
         }
 
-        $pos = iconv_strrpos($haystack, $needle, $encoding);
+        $pos = '' !== $needle || 80000 > \PHP_VERSION_ID
+            ? \iconv_strrpos($haystack, $needle, $encoding)
+            : self::mb_strlen($haystack, $encoding);
 
         return false !== $pos ? $offset + $pos : false;
     }
 
     public static function mb_str_split($string, $split_length = 1, $encoding = null)
     {
-        if (null !== $string && !\is_scalar($string) && !(\is_object($string) && \method_exists($string, '__toString'))) {
-            trigger_error('mb_str_split() expects parameter 1 to be string, '.\gettype($string).' given', E_USER_WARNING);
+        if (null !== $string && !is_scalar($string) && !(\is_object($string) && method_exists($string, '__toString'))) {
+            trigger_error('mb_str_split() expects parameter 1 to be string, '.\gettype($string).' given', \E_USER_WARNING);
 
             return null;
         }
 
-        if ($split_length < 1) {
-            trigger_error('The length of each segment must be greater than zero', E_USER_WARNING);
+        if (1 > $split_length = (int) $split_length) {
+            if (80000 > \PHP_VERSION_ID) {
+                trigger_error('The length of each segment must be greater than zero', \E_USER_WARNING);
+                return false;
+            }
 
-            return false;
+            throw new \ValueError('Argument #2 ($length) must be greater than 0');
         }
 
         if (null === $encoding) {
             $encoding = mb_internal_encoding();
         }
 
-        $result = array();
+        if ('UTF-8' === $encoding = self::getEncoding($encoding)) {
+            $rx = '/(';
+            while (65535 < $split_length) {
+                $rx .= '.{65535}';
+                $split_length -= 65535;
+            }
+            $rx .= '.{'.$split_length.'})/us';
+
+            return preg_split($rx, $string, -1, \PREG_SPLIT_DELIM_CAPTURE | \PREG_SPLIT_NO_EMPTY);
+        }
+
+        $result = [];
         $length = mb_strlen($string, $encoding);
 
         for ($i = 0; $i < $length; $i += $split_length) {
@@ -554,21 +583,30 @@ public static function mb_str_split($string, $split_length = 1, $encoding = null
 
     public static function mb_strtolower($s, $encoding = null)
     {
-        return self::mb_convert_case($s, MB_CASE_LOWER, $encoding);
+        return self::mb_convert_case($s, \MB_CASE_LOWER, $encoding);
     }
 
     public static function mb_strtoupper($s, $encoding = null)
     {
-        return self::mb_convert_case($s, MB_CASE_UPPER, $encoding);
+        return self::mb_convert_case($s, \MB_CASE_UPPER, $encoding);
     }
 
     public static function mb_substitute_character($c = null)
     {
+        if (null === $c) {
+            return 'none';
+        }
         if (0 === strcasecmp($c, 'none')) {
             return true;
         }
+        if (80000 > \PHP_VERSION_ID) {
+            return false;
+        }
+        if (\is_int($c) || 'long' === $c || 'entity' === $c) {
+            return false;
+        }
 
-        return null !== $c ? false : 'none';
+        throw new \ValueError('Argument #1 ($substitute_character) must be "none", "long", "entity" or a valid codepoint');
     }
 
     public static function mb_substr($s, $start, $length = null, $encoding = null)
@@ -579,7 +617,7 @@ public static function mb_substr($s, $start, $length = null, $encoding = null)
         }
 
         if ($start < 0) {
-            $start = iconv_strlen($s, $encoding) + $start;
+            $start = \iconv_strlen($s, $encoding) + $start;
             if ($start < 0) {
                 $start = 0;
             }
@@ -588,13 +626,13 @@ public static function mb_substr($s, $start, $length = null, $encoding = null)
         if (null === $length) {
             $length = 2147483647;
         } elseif ($length < 0) {
-            $length = iconv_strlen($s, $encoding) + $length - $start;
+            $length = \iconv_strlen($s, $encoding) + $length - $start;
             if ($length < 0) {
                 return '';
             }
         }
 
-        return (string) iconv_substr($s, $start, $length, $encoding);
+        return (string) \iconv_substr($s, $start, $length, $encoding);
     }
 
     public static function mb_stripos($haystack, $needle, $offset = 0, $encoding = null)
@@ -616,10 +654,11 @@ public static function mb_strrchr($haystack, $needle, $part = false, $encoding =
     {
         $encoding = self::getEncoding($encoding);
         if ('CP850' === $encoding || 'ASCII' === $encoding) {
-            return strrchr($haystack, $needle, $part);
+            $pos = strrpos($haystack, $needle);
+        } else {
+            $needle = self::mb_substr($needle, 0, 1, $encoding);
+            $pos = \iconv_strrpos($haystack, $needle, $encoding);
         }
-        $needle = self::mb_substr($needle, 0, 1, $encoding);
-        $pos = iconv_strrpos($haystack, $needle, $encoding);
 
         return self::getSubpart($pos, $part, $haystack, $encoding);
     }
@@ -655,7 +694,7 @@ public static function mb_strstr($haystack, $needle, $part = false, $encoding =
 
     public static function mb_get_info($type = 'all')
     {
-        $info = array(
+        $info = [
             'internal_encoding' => self::$internalEncoding,
             'http_output' => 'pass',
             'http_output_conv_mimetypes' => '^(text/|application/xhtml\+xml)',
@@ -670,7 +709,7 @@ public static function mb_get_info($type = 'all')
             'detect_order' => self::$encodingList,
             'substitute_character' => 'none',
             'strict_detection' => 'Off',
-        );
+        ];
 
         if ('all' === $type) {
             return $info;
@@ -697,12 +736,12 @@ public static function mb_strwidth($s, $encoding = null)
         $encoding = self::getEncoding($encoding);
 
         if ('UTF-8' !== $encoding) {
-            $s = iconv($encoding, 'UTF-8//IGNORE', $s);
+            $s = \iconv($encoding, 'UTF-8//IGNORE', $s);
         }
 
         $s = preg_replace('/[\x{1100}-\x{115F}\x{2329}\x{232A}\x{2E80}-\x{303E}\x{3040}-\x{A4CF}\x{AC00}-\x{D7A3}\x{F900}-\x{FAFF}\x{FE10}-\x{FE19}\x{FE30}-\x{FE6F}\x{FF00}-\x{FF60}\x{FFE0}-\x{FFE6}\x{20000}-\x{2FFFD}\x{30000}-\x{3FFFD}]/u', '', $s, -1, $wide);
 
-        return ($wide << 1) + iconv_strlen($s, 'UTF-8');
+        return ($wide << 1) + \iconv_strlen($s, 'UTF-8');
     }
 
     public static function mb_substr_count($haystack, $needle, $encoding = null)
@@ -774,7 +813,7 @@ private static function html_encoding_callback(array $m)
     {
         $i = 1;
         $entities = '';
-        $m = unpack('C*', htmlentities($m[0], ENT_COMPAT, 'UTF-8'));
+        $m = unpack('C*', htmlentities($m[0], \ENT_COMPAT, 'UTF-8'));
 
         while (isset($m[$i])) {
             if (0x80 > $m[$i]) {
@@ -797,7 +836,7 @@ private static function html_encoding_callback(array $m)
 
     private static function title_case(array $s)
     {
-        return self::mb_convert_case($s[1], MB_CASE_UPPER, 'UTF-8').self::mb_convert_case($s[2], MB_CASE_LOWER, 'UTF-8');
+        return self::mb_convert_case($s[1], \MB_CASE_UPPER, 'UTF-8').self::mb_convert_case($s[2], \MB_CASE_LOWER, 'UTF-8');
     }
 
     private static function getData($file)
@@ -815,11 +854,16 @@ private static function getEncoding($encoding)
             return self::$internalEncoding;
         }
 
+        if ('UTF-8' === $encoding) {
+            return 'UTF-8';
+        }
+
         $encoding = strtoupper($encoding);
 
         if ('8BIT' === $encoding || 'BINARY' === $encoding) {
             return 'CP850';
         }
+
         if ('UTF8' === $encoding) {
             return 'UTF-8';
         }
diff --git a/README.md b/README.md
index 342e828..478b40d 100644
--- a/README.md
+++ b/README.md
@@ -2,10 +2,10 @@ Symfony Polyfill / Mbstring
 ===========================
 
 This component provides a partial, native PHP implementation for the
-[Mbstring](http://php.net/mbstring) extension.
+[Mbstring](https://php.net/mbstring) extension.
 
 More information can be found in the
-[main Polyfill README](https://github.com/symfony/polyfill/blob/master/README.md).
+[main Polyfill README](https://github.com/symfony/polyfill/blob/main/README.md).
 
 License
 =======
diff --git a/Resources/unidata/lowerCase.php b/Resources/unidata/lowerCase.php
index e6fbfa6..fac60b0 100644
--- a/Resources/unidata/lowerCase.php
+++ b/Resources/unidata/lowerCase.php
@@ -1,6 +1,6 @@
 <?php
 
-return array(
+return array (
   'A' => 'a',
   'B' => 'b',
   'C' => 'c',
@@ -81,7 +81,7 @@
   'Ī' => 'ī',
   'Ĭ' => 'ĭ',
   'Į' => 'į',
-  'İ' => 'i',
+  'İ' => 'i̇',
   'IJ' => 'ij',
   'Ĵ' => 'ĵ',
   'Ķ' => 'ķ',
@@ -510,6 +510,138 @@
   'Ⴥ' => 'ⴥ',
   'Ⴧ' => 'ⴧ',
   'Ⴭ' => 'ⴭ',
+  'Ꭰ' => 'ꭰ',
+  'Ꭱ' => 'ꭱ',
+  'Ꭲ' => 'ꭲ',
+  'Ꭳ' => 'ꭳ',
+  'Ꭴ' => 'ꭴ',
+  'Ꭵ' => 'ꭵ',
+  'Ꭶ' => 'ꭶ',
+  'Ꭷ' => 'ꭷ',
+  'Ꭸ' => 'ꭸ',
+  'Ꭹ' => 'ꭹ',
+  'Ꭺ' => 'ꭺ',
+  'Ꭻ' => 'ꭻ',
+  'Ꭼ' => 'ꭼ',
+  'Ꭽ' => 'ꭽ',
+  'Ꭾ' => 'ꭾ',
+  'Ꭿ' => 'ꭿ',
+  'Ꮀ' => 'ꮀ',
+  'Ꮁ' => 'ꮁ',
+  'Ꮂ' => 'ꮂ',
+  'Ꮃ' => 'ꮃ',
+  'Ꮄ' => 'ꮄ',
+  'Ꮅ' => 'ꮅ',
+  'Ꮆ' => 'ꮆ',
+  'Ꮇ' => 'ꮇ',
+  'Ꮈ' => 'ꮈ',
+  'Ꮉ' => 'ꮉ',
+  'Ꮊ' => 'ꮊ',
+  'Ꮋ' => 'ꮋ',
+  'Ꮌ' => 'ꮌ',
+  'Ꮍ' => 'ꮍ',
+  'Ꮎ' => 'ꮎ',
+  'Ꮏ' => 'ꮏ',
+  'Ꮐ' => 'ꮐ',
+  'Ꮑ' => 'ꮑ',
+  'Ꮒ' => 'ꮒ',
+  'Ꮓ' => 'ꮓ',
+  'Ꮔ' => 'ꮔ',
+  'Ꮕ' => 'ꮕ',
+  'Ꮖ' => 'ꮖ',
+  'Ꮗ' => 'ꮗ',
+  'Ꮘ' => 'ꮘ',
+  'Ꮙ' => 'ꮙ',
+  'Ꮚ' => 'ꮚ',
+  'Ꮛ' => 'ꮛ',
+  'Ꮜ' => 'ꮜ',
+  'Ꮝ' => 'ꮝ',
+  'Ꮞ' => 'ꮞ',
+  'Ꮟ' => 'ꮟ',
+  'Ꮠ' => 'ꮠ',
+  'Ꮡ' => 'ꮡ',
+  'Ꮢ' => 'ꮢ',
+  'Ꮣ' => 'ꮣ',
+  'Ꮤ' => 'ꮤ',
+  'Ꮥ' => 'ꮥ',
+  'Ꮦ' => 'ꮦ',
+  'Ꮧ' => 'ꮧ',
+  'Ꮨ' => 'ꮨ',
+  'Ꮩ' => 'ꮩ',
+  'Ꮪ' => 'ꮪ',
+  'Ꮫ' => 'ꮫ',
+  'Ꮬ' => 'ꮬ',
+  'Ꮭ' => 'ꮭ',
+  'Ꮮ' => 'ꮮ',
+  'Ꮯ' => 'ꮯ',
+  'Ꮰ' => 'ꮰ',
+  'Ꮱ' => 'ꮱ',
+  'Ꮲ' => 'ꮲ',
+  'Ꮳ' => 'ꮳ',
+  'Ꮴ' => 'ꮴ',
+  'Ꮵ' => 'ꮵ',
+  'Ꮶ' => 'ꮶ',
+  'Ꮷ' => 'ꮷ',
+  'Ꮸ' => 'ꮸ',
+  'Ꮹ' => 'ꮹ',
+  'Ꮺ' => 'ꮺ',
+  'Ꮻ' => 'ꮻ',
+  'Ꮼ' => 'ꮼ',
+  'Ꮽ' => 'ꮽ',
+  'Ꮾ' => 'ꮾ',
+  'Ꮿ' => 'ꮿ',
+  'Ᏸ' => 'ᏸ',
+  'Ᏹ' => 'ᏹ',
+  'Ᏺ' => 'ᏺ',
+  'Ᏻ' => 'ᏻ',
+  'Ᏼ' => 'ᏼ',
+  'Ᏽ' => 'ᏽ',
+  'Ა' => 'ა',
+  'Ბ' => 'ბ',
+  'Გ' => 'გ',
+  'Დ' => 'დ',
+  'Ე' => 'ე',
+  'Ვ' => 'ვ',
+  'Ზ' => 'ზ',
+  'Თ' => 'თ',
+  'Ი' => 'ი',
+  'Კ' => 'კ',
+  'Ლ' => 'ლ',
+  'Მ' => 'მ',
+  'Ნ' => 'ნ',
+  'Ო' => 'ო',
+  'Პ' => 'პ',
+  'Ჟ' => 'ჟ',
+  'Რ' => 'რ',
+  'Ს' => 'ს',
+  'Ტ' => 'ტ',
+  'Უ' => 'უ',
+  'Ფ' => 'ფ',
+  'Ქ' => 'ქ',
+  'Ღ' => 'ღ',
+  'Ყ' => 'ყ',
+  'Შ' => 'შ',
+  'Ჩ' => 'ჩ',
+  'Ც' => 'ც',
+  'Ძ' => 'ძ',
+  'Წ' => 'წ',
+  'Ჭ' => 'ჭ',
+  'Ხ' => 'ხ',
+  'Ჯ' => 'ჯ',
+  'Ჰ' => 'ჰ',
+  'Ჱ' => 'ჱ',
+  'Ჲ' => 'ჲ',
+  'Ჳ' => 'ჳ',
+  'Ჴ' => 'ჴ',
+  'Ჵ' => 'ჵ',
+  'Ჶ' => 'ჶ',
+  'Ჷ' => 'ჷ',
+  'Ჸ' => 'ჸ',
+  'Ჹ' => 'ჹ',
+  'Ჺ' => 'ჺ',
+  'Ჽ' => 'ჽ',
+  'Ჾ' => 'ჾ',
+  'Ჿ' => 'ჿ',
   'Ḁ' => 'ḁ',
   'Ḃ' => 'ḃ',
   'Ḅ' => 'ḅ',
@@ -993,8 +1125,24 @@
   'Ɜ' => 'ɜ',
   'Ɡ' => 'ɡ',
   'Ɬ' => 'ɬ',
+  'Ɪ' => 'ɪ',
   'Ʞ' => 'ʞ',
   'Ʇ' => 'ʇ',
+  'Ʝ' => 'ʝ',
+  'Ꭓ' => 'ꭓ',
+  'Ꞵ' => 'ꞵ',
+  'Ꞷ' => 'ꞷ',
+  'Ꞹ' => 'ꞹ',
+  'Ꞻ' => 'ꞻ',
+  'Ꞽ' => 'ꞽ',
+  'Ꞿ' => 'ꞿ',
+  'Ꟃ' => 'ꟃ',
+  'Ꞔ' => 'ꞔ',
+  'Ʂ' => 'ʂ',
+  'Ᶎ' => 'ᶎ',
+  'Ꟈ' => 'ꟈ',
+  'Ꟊ' => 'ꟊ',
+  'Ꟶ' => 'ꟶ',
   'Ａ' => 'ａ',
   'Ｂ' => 'ｂ',
   'Ｃ' => 'ｃ',
@@ -1061,6 +1209,93 @@
   '𐐥' => '𐑍',
   '𐐦' => '𐑎',
   '𐐧' => '𐑏',
+  '𐒰' => '𐓘',
+  '𐒱' => '𐓙',
+  '𐒲' => '𐓚',
+  '𐒳' => '𐓛',
+  '𐒴' => '𐓜',
+  '𐒵' => '𐓝',
+  '𐒶' => '𐓞',
+  '𐒷' => '𐓟',
+  '𐒸' => '𐓠',
+  '𐒹' => '𐓡',
+  '𐒺' => '𐓢',
+  '𐒻' => '𐓣',
+  '𐒼' => '𐓤',
+  '𐒽' => '𐓥',
+  '𐒾' => '𐓦',
+  '𐒿' => '𐓧',
+  '𐓀' => '𐓨',
+  '𐓁' => '𐓩',
+  '𐓂' => '𐓪',
+  '𐓃' => '𐓫',
+  '𐓄' => '𐓬',
+  '𐓅' => '𐓭',
+  '𐓆' => '𐓮',
+  '𐓇' => '𐓯',
+  '𐓈' => '𐓰',
+  '𐓉' => '𐓱',
+  '𐓊' => '𐓲',
+  '𐓋' => '𐓳',
+  '𐓌' => '𐓴',
+  '𐓍' => '𐓵',
+  '𐓎' => '𐓶',
+  '𐓏' => '𐓷',
+  '𐓐' => '𐓸',
+  '𐓑' => '𐓹',
+  '𐓒' => '𐓺',
+  '𐓓' => '𐓻',
+  '𐲀' => '𐳀',
+  '𐲁' => '𐳁',
+  '𐲂' => '𐳂',
+  '𐲃' => '𐳃',
+  '𐲄' => '𐳄',
+  '𐲅' => '𐳅',
+  '𐲆' => '𐳆',
+  '𐲇' => '𐳇',
+  '𐲈' => '𐳈',
+  '𐲉' => '𐳉',
+  '𐲊' => '𐳊',
+  '𐲋' => '𐳋',
+  '𐲌' => '𐳌',
+  '𐲍' => '𐳍',
+  '𐲎' => '𐳎',
+  '𐲏' => '𐳏',
+  '𐲐' => '𐳐',
+  '𐲑' => '𐳑',
+  '𐲒' => '𐳒',
+  '𐲓' => '𐳓',
+  '𐲔' => '𐳔',
+  '𐲕' => '𐳕',
+  '𐲖' => '𐳖',
+  '𐲗' => '𐳗',
+  '𐲘' => '𐳘',
+  '𐲙' => '𐳙',
+  '𐲚' => '𐳚',
+  '𐲛' => '𐳛',
+  '𐲜' => '𐳜',
+  '𐲝' => '𐳝',
+  '𐲞' => '𐳞',
+  '𐲟' => '𐳟',
+  '𐲠' => '𐳠',
+  '𐲡' => '𐳡',
+  '𐲢' => '𐳢',
+  '𐲣' => '𐳣',
+  '𐲤' => '𐳤',
+  '𐲥' => '𐳥',
+  '𐲦' => '𐳦',
+  '𐲧' => '𐳧',
+  '𐲨' => '𐳨',
+  '𐲩' => '𐳩',
+  '𐲪' => '𐳪',
+  '𐲫' => '𐳫',
+  '𐲬' => '𐳬',
+  '𐲭' => '𐳭',
+  '𐲮' => '𐳮',
+  '𐲯' => '𐳯',
+  '𐲰' => '𐳰',
+  '𐲱' => '𐳱',
+  '𐲲' => '𐳲',
   '𑢠' => '𑣀',
   '𑢡' => '𑣁',
   '𑢢' => '𑣂',
@@ -1093,4 +1328,70 @@
   '𑢽' => '𑣝',
   '𑢾' => '𑣞',
   '𑢿' => '𑣟',
+  '𖹀' => '𖹠',
+  '𖹁' => '𖹡',
+  '𖹂' => '𖹢',
+  '𖹃' => '𖹣',
+  '𖹄' => '𖹤',
+  '𖹅' => '𖹥',
+  '𖹆' => '𖹦',
+  '𖹇' => '𖹧',
+  '𖹈' => '𖹨',
+  '𖹉' => '𖹩',
+  '𖹊' => '𖹪',
+  '𖹋' => '𖹫',
+  '𖹌' => '𖹬',
+  '𖹍' => '𖹭',
+  '𖹎' => '𖹮',
+  '𖹏' => '𖹯',
+  '𖹐' => '𖹰',
+  '𖹑' => '𖹱',
+  '𖹒' => '𖹲',
+  '𖹓' => '𖹳',
+  '𖹔' => '𖹴',
+  '𖹕' => '𖹵',
+  '𖹖' => '𖹶',
+  '𖹗' => '𖹷',
+  '𖹘' => '𖹸',
+  '𖹙' => '𖹹',
+  '𖹚' => '𖹺',
+  '𖹛' => '𖹻',
+  '𖹜' => '𖹼',
+  '𖹝' => '𖹽',
+  '𖹞' => '𖹾',
+  '𖹟' => '𖹿',
+  '𞤀' => '𞤢',
+  '𞤁' => '𞤣',
+  '𞤂' => '𞤤',
+  '𞤃' => '𞤥',
+  '𞤄' => '𞤦',
+  '𞤅' => '𞤧',
+  '𞤆' => '𞤨',
+  '𞤇' => '𞤩',
+  '𞤈' => '𞤪',
+  '𞤉' => '𞤫',
+  '𞤊' => '𞤬',
+  '𞤋' => '𞤭',
+  '𞤌' => '𞤮',
+  '𞤍' => '𞤯',
+  '𞤎' => '𞤰',
+  '𞤏' => '𞤱',
+  '𞤐' => '𞤲',
+  '𞤑' => '𞤳',
+  '𞤒' => '𞤴',
+  '𞤓' => '𞤵',
+  '𞤔' => '𞤶',
+  '𞤕' => '𞤷',
+  '𞤖' => '𞤸',
+  '𞤗' => '𞤹',
+  '𞤘' => '𞤺',
+  '𞤙' => '𞤻',
+  '𞤚' => '𞤼',
+  '𞤛' => '𞤽',
+  '𞤜' => '𞤾',
+  '𞤝' => '𞤿',
+  '𞤞' => '𞥀',
+  '𞤟' => '𞥁',
+  '𞤠' => '𞥂',
+  '𞤡' => '𞥃',
 );
diff --git a/Resources/unidata/upperCase.php b/Resources/unidata/upperCase.php
index b8103b2..56b9cb8 100644
--- a/Resources/unidata/upperCase.php
+++ b/Resources/unidata/upperCase.php
@@ -1,6 +1,6 @@
 <?php
 
-return array(
+return array (
   'a' => 'A',
   'b' => 'B',
   'c' => 'C',
@@ -225,6 +225,7 @@
   'ɦ' => 'Ɦ',
   'ɨ' => 'Ɨ',
   'ɩ' => 'Ɩ',
+  'ɪ' => 'Ɪ',
   'ɫ' => 'Ɫ',
   'ɬ' => 'Ɬ',
   'ɯ' => 'Ɯ',
@@ -233,6 +234,7 @@
   'ɵ' => 'Ɵ',
   'ɽ' => 'Ɽ',
   'ʀ' => 'Ʀ',
+  'ʂ' => 'Ʂ',
   'ʃ' => 'Ʃ',
   'ʇ' => 'Ʇ',
   'ʈ' => 'Ʈ',
@@ -241,6 +243,7 @@
   'ʋ' => 'Ʋ',
   'ʌ' => 'Ʌ',
   'ʒ' => 'Ʒ',
+  'ʝ' => 'Ʝ',
   'ʞ' => 'Ʞ',
   'ͅ' => 'Ι',
   'ͱ' => 'Ͱ',
@@ -493,8 +496,70 @@
   'ք' => 'Ք',
   'օ' => 'Օ',
   'ֆ' => 'Ֆ',
+  'ა' => 'Ა',
+  'ბ' => 'Ბ',
+  'გ' => 'Გ',
+  'დ' => 'Დ',
+  'ე' => 'Ე',
+  'ვ' => 'Ვ',
+  'ზ' => 'Ზ',
+  'თ' => 'Თ',
+  'ი' => 'Ი',
+  'კ' => 'Კ',
+  'ლ' => 'Ლ',
+  'მ' => 'Მ',
+  'ნ' => 'Ნ',
+  'ო' => 'Ო',
+  'პ' => 'Პ',
+  'ჟ' => 'Ჟ',
+  'რ' => 'Რ',
+  'ს' => 'Ს',
+  'ტ' => 'Ტ',
+  'უ' => 'Უ',
+  'ფ' => 'Ფ',
+  'ქ' => 'Ქ',
+  'ღ' => 'Ღ',
+  'ყ' => 'Ყ',
+  'შ' => 'Შ',
+  'ჩ' => 'Ჩ',
+  'ც' => 'Ც',
+  'ძ' => 'Ძ',
+  'წ' => 'Წ',
+  'ჭ' => 'Ჭ',
+  'ხ' => 'Ხ',
+  'ჯ' => 'Ჯ',
+  'ჰ' => 'Ჰ',
+  'ჱ' => 'Ჱ',
+  'ჲ' => 'Ჲ',
+  'ჳ' => 'Ჳ',
+  'ჴ' => 'Ჴ',
+  'ჵ' => 'Ჵ',
+  'ჶ' => 'Ჶ',
+  'ჷ' => 'Ჷ',
+  'ჸ' => 'Ჸ',
+  'ჹ' => 'Ჹ',
+  'ჺ' => 'Ჺ',
+  'ჽ' => 'Ჽ',
+  'ჾ' => 'Ჾ',
+  'ჿ' => 'Ჿ',
+  'ᏸ' => 'Ᏸ',
+  'ᏹ' => 'Ᏹ',
+  'ᏺ' => 'Ᏺ',
+  'ᏻ' => 'Ᏻ',
+  'ᏼ' => 'Ᏼ',
+  'ᏽ' => 'Ᏽ',
+  'ᲀ' => 'В',
+  'ᲁ' => 'Д',
+  'ᲂ' => 'О',
+  'ᲃ' => 'С',
+  'ᲄ' => 'Т',
+  'ᲅ' => 'Т',
+  'ᲆ' => 'Ъ',
+  'ᲇ' => 'Ѣ',
+  'ᲈ' => 'Ꙋ',
   'ᵹ' => 'Ᵹ',
   'ᵽ' => 'Ᵽ',
+  'ᶎ' => 'Ᶎ',
   'ḁ' => 'Ḁ',
   'ḃ' => 'Ḃ',
   'ḅ' => 'Ḅ',
@@ -681,41 +746,41 @@
   'ύ' => 'Ύ',
   'ὼ' => 'Ὼ',
   'ώ' => 'Ώ',
-  'ᾀ' => 'ᾈ',
-  'ᾁ' => 'ᾉ',
-  'ᾂ' => 'ᾊ',
-  'ᾃ' => 'ᾋ',
-  'ᾄ' => 'ᾌ',
-  'ᾅ' => 'ᾍ',
-  'ᾆ' => 'ᾎ',
-  'ᾇ' => 'ᾏ',
-  'ᾐ' => 'ᾘ',
-  'ᾑ' => 'ᾙ',
-  'ᾒ' => 'ᾚ',
-  'ᾓ' => 'ᾛ',
-  'ᾔ' => 'ᾜ',
-  'ᾕ' => 'ᾝ',
-  'ᾖ' => 'ᾞ',
-  'ᾗ' => 'ᾟ',
-  'ᾠ' => 'ᾨ',
-  'ᾡ' => 'ᾩ',
-  'ᾢ' => 'ᾪ',
-  'ᾣ' => 'ᾫ',
-  'ᾤ' => 'ᾬ',
-  'ᾥ' => 'ᾭ',
-  'ᾦ' => 'ᾮ',
-  'ᾧ' => 'ᾯ',
+  'ᾀ' => 'ἈΙ',
+  'ᾁ' => 'ἉΙ',
+  'ᾂ' => 'ἊΙ',
+  'ᾃ' => 'ἋΙ',
+  'ᾄ' => 'ἌΙ',
+  'ᾅ' => 'ἍΙ',
+  'ᾆ' => 'ἎΙ',
+  'ᾇ' => 'ἏΙ',
+  'ᾐ' => 'ἨΙ',
+  'ᾑ' => 'ἩΙ',
+  'ᾒ' => 'ἪΙ',
+  'ᾓ' => 'ἫΙ',
+  'ᾔ' => 'ἬΙ',
+  'ᾕ' => 'ἭΙ',
+  'ᾖ' => 'ἮΙ',
+  'ᾗ' => 'ἯΙ',
+  'ᾠ' => 'ὨΙ',
+  'ᾡ' => 'ὩΙ',
+  'ᾢ' => 'ὪΙ',
+  'ᾣ' => 'ὫΙ',
+  'ᾤ' => 'ὬΙ',
+  'ᾥ' => 'ὭΙ',
+  'ᾦ' => 'ὮΙ',
+  'ᾧ' => 'ὯΙ',
   'ᾰ' => 'Ᾰ',
   'ᾱ' => 'Ᾱ',
-  'ᾳ' => 'ᾼ',
+  'ᾳ' => 'ΑΙ',
   'ι' => 'Ι',
-  'ῃ' => 'ῌ',
+  'ῃ' => 'ΗΙ',
   'ῐ' => 'Ῐ',
   'ῑ' => 'Ῑ',
   'ῠ' => 'Ῠ',
   'ῡ' => 'Ῡ',
   'ῥ' => 'Ῥ',
-  'ῳ' => 'ῼ',
+  'ῳ' => 'ΩΙ',
   'ⅎ' => 'Ⅎ',
   'ⅰ' => 'Ⅰ',
   'ⅱ' => 'Ⅱ',
@@ -993,6 +1058,7 @@
   'ꞌ' => 'Ꞌ',
   'ꞑ' => 'Ꞑ',
   'ꞓ' => 'Ꞓ',
+  'ꞔ' => 'Ꞔ',
   'ꞗ' => 'Ꞗ',
   'ꞙ' => 'Ꞙ',
   'ꞛ' => 'Ꞛ',
@@ -1003,6 +1069,97 @@
   'ꞥ' => 'Ꞥ',
   'ꞧ' => 'Ꞧ',
   'ꞩ' => 'Ꞩ',
+  'ꞵ' => 'Ꞵ',
+  'ꞷ' => 'Ꞷ',
+  'ꞹ' => 'Ꞹ',
+  'ꞻ' => 'Ꞻ',
+  'ꞽ' => 'Ꞽ',
+  'ꞿ' => 'Ꞿ',
+  'ꟃ' => 'Ꟃ',
+  'ꟈ' => 'Ꟈ',
+  'ꟊ' => 'Ꟊ',
+  'ꟶ' => 'Ꟶ',
+  'ꭓ' => 'Ꭓ',
+  'ꭰ' => 'Ꭰ',
+  'ꭱ' => 'Ꭱ',
+  'ꭲ' => 'Ꭲ',
+  'ꭳ' => 'Ꭳ',
+  'ꭴ' => 'Ꭴ',
+  'ꭵ' => 'Ꭵ',
+  'ꭶ' => 'Ꭶ',
+  'ꭷ' => 'Ꭷ',
+  'ꭸ' => 'Ꭸ',
+  'ꭹ' => 'Ꭹ',
+  'ꭺ' => 'Ꭺ',
+  'ꭻ' => 'Ꭻ',
+  'ꭼ' => 'Ꭼ',
+  'ꭽ' => 'Ꭽ',
+  'ꭾ' => 'Ꭾ',
+  'ꭿ' => 'Ꭿ',
+  'ꮀ' => 'Ꮀ',
+  'ꮁ' => 'Ꮁ',
+  'ꮂ' => 'Ꮂ',
+  'ꮃ' => 'Ꮃ',
+  'ꮄ' => 'Ꮄ',
+  'ꮅ' => 'Ꮅ',
+  'ꮆ' => 'Ꮆ',
+  'ꮇ' => 'Ꮇ',
+  'ꮈ' => 'Ꮈ',
+  'ꮉ' => 'Ꮉ',
+  'ꮊ' => 'Ꮊ',
+  'ꮋ' => 'Ꮋ',
+  'ꮌ' => 'Ꮌ',
+  'ꮍ' => 'Ꮍ',
+  'ꮎ' => 'Ꮎ',
+  'ꮏ' => 'Ꮏ',
+  'ꮐ' => 'Ꮐ',
+  'ꮑ' => 'Ꮑ',
+  'ꮒ' => 'Ꮒ',
+  'ꮓ' => 'Ꮓ',
+  'ꮔ' => 'Ꮔ',
+  'ꮕ' => 'Ꮕ',
+  'ꮖ' => 'Ꮖ',
+  'ꮗ' => 'Ꮗ',
+  'ꮘ' => 'Ꮘ',
+  'ꮙ' => 'Ꮙ',
+  'ꮚ' => 'Ꮚ',
+  'ꮛ' => 'Ꮛ',
+  'ꮜ' => 'Ꮜ',
+  'ꮝ' => 'Ꮝ',
+  'ꮞ' => 'Ꮞ',
+  'ꮟ' => 'Ꮟ',
+  'ꮠ' => 'Ꮠ',
+  'ꮡ' => 'Ꮡ',
+  'ꮢ' => 'Ꮢ',
+  'ꮣ' => 'Ꮣ',
+  'ꮤ' => 'Ꮤ',
+  'ꮥ' => 'Ꮥ',
+  'ꮦ' => 'Ꮦ',
+  'ꮧ' => 'Ꮧ',
+  'ꮨ' => 'Ꮨ',
+  'ꮩ' => 'Ꮩ',
+  'ꮪ' => 'Ꮪ',
+  'ꮫ' => 'Ꮫ',
+  'ꮬ' => 'Ꮬ',
+  'ꮭ' => 'Ꮭ',
+  'ꮮ' => 'Ꮮ',
+  'ꮯ' => 'Ꮯ',
+  'ꮰ' => 'Ꮰ',
+  'ꮱ' => 'Ꮱ',
+  'ꮲ' => 'Ꮲ',
+  'ꮳ' => 'Ꮳ',
+  'ꮴ' => 'Ꮴ',
+  'ꮵ' => 'Ꮵ',
+  'ꮶ' => 'Ꮶ',
+  'ꮷ' => 'Ꮷ',
+  'ꮸ' => 'Ꮸ',
+  'ꮹ' => 'Ꮹ',
+  'ꮺ' => 'Ꮺ',
+  'ꮻ' => 'Ꮻ',
+  'ꮼ' => 'Ꮼ',
+  'ꮽ' => 'Ꮽ',
+  'ꮾ' => 'Ꮾ',
+  'ꮿ' => 'Ꮿ',
   'ａ' => 'Ａ',
   'ｂ' => 'Ｂ',
   'ｃ' => 'Ｃ',
@@ -1069,6 +1226,93 @@
   '𐑍' => '𐐥',
   '𐑎' => '𐐦',
   '𐑏' => '𐐧',
+  '𐓘' => '𐒰',
+  '𐓙' => '𐒱',
+  '𐓚' => '𐒲',
+  '𐓛' => '𐒳',
+  '𐓜' => '𐒴',
+  '𐓝' => '𐒵',
+  '𐓞' => '𐒶',
+  '𐓟' => '𐒷',
+  '𐓠' => '𐒸',
+  '𐓡' => '𐒹',
+  '𐓢' => '𐒺',
+  '𐓣' => '𐒻',
+  '𐓤' => '𐒼',
+  '𐓥' => '𐒽',
+  '𐓦' => '𐒾',
+  '𐓧' => '𐒿',
+  '𐓨' => '𐓀',
+  '𐓩' => '𐓁',
+  '𐓪' => '𐓂',
+  '𐓫' => '𐓃',
+  '𐓬' => '𐓄',
+  '𐓭' => '𐓅',
+  '𐓮' => '𐓆',
+  '𐓯' => '𐓇',
+  '𐓰' => '𐓈',
+  '𐓱' => '𐓉',
+  '𐓲' => '𐓊',
+  '𐓳' => '𐓋',
+  '𐓴' => '𐓌',
+  '𐓵' => '𐓍',
+  '𐓶' => '𐓎',
+  '𐓷' => '𐓏',
+  '𐓸' => '𐓐',
+  '𐓹' => '𐓑',
+  '𐓺' => '𐓒',
+  '𐓻' => '𐓓',
+  '𐳀' => '𐲀',
+  '𐳁' => '𐲁',
+  '𐳂' => '𐲂',
+  '𐳃' => '𐲃',
+  '𐳄' => '𐲄',
+  '𐳅' => '𐲅',
+  '𐳆' => '𐲆',
+  '𐳇' => '𐲇',
+  '𐳈' => '𐲈',
+  '𐳉' => '𐲉',
+  '𐳊' => '𐲊',
+  '𐳋' => '𐲋',
+  '𐳌' => '𐲌',
+  '𐳍' => '𐲍',
+  '𐳎' => '𐲎',
+  '𐳏' => '𐲏',
+  '𐳐' => '𐲐',
+  '𐳑' => '𐲑',
+  '𐳒' => '𐲒',
+  '𐳓' => '𐲓',
+  '𐳔' => '𐲔',
+  '𐳕' => '𐲕',
+  '𐳖' => '𐲖',
+  '𐳗' => '𐲗',
+  '𐳘' => '𐲘',
+  '𐳙' => '𐲙',
+  '𐳚' => '𐲚',
+  '𐳛' => '𐲛',
+  '𐳜' => '𐲜',
+  '𐳝' => '𐲝',
+  '𐳞' => '𐲞',
+  '𐳟' => '𐲟',
+  '𐳠' => '𐲠',
+  '𐳡' => '𐲡',
+  '𐳢' => '𐲢',
+  '𐳣' => '𐲣',
+  '𐳤' => '𐲤',
+  '𐳥' => '𐲥',
+  '𐳦' => '𐲦',
+  '𐳧' => '𐲧',
+  '𐳨' => '𐲨',
+  '𐳩' => '𐲩',
+  '𐳪' => '𐲪',
+  '𐳫' => '𐲫',
+  '𐳬' => '𐲬',
+  '𐳭' => '𐲭',
+  '𐳮' => '𐲮',
+  '𐳯' => '𐲯',
+  '𐳰' => '𐲰',
+  '𐳱' => '𐲱',
+  '𐳲' => '𐲲',
   '𑣀' => '𑢠',
   '𑣁' => '𑢡',
   '𑣂' => '𑢢',
@@ -1101,4 +1345,145 @@
   '𑣝' => '𑢽',
   '𑣞' => '𑢾',
   '𑣟' => '𑢿',
+  '𖹠' => '𖹀',
+  '𖹡' => '𖹁',
+  '𖹢' => '𖹂',
+  '𖹣' => '𖹃',
+  '𖹤' => '𖹄',
+  '𖹥' => '𖹅',
+  '𖹦' => '𖹆',
+  '𖹧' => '𖹇',
+  '𖹨' => '𖹈',
+  '𖹩' => '𖹉',
+  '𖹪' => '𖹊',
+  '𖹫' => '𖹋',
+  '𖹬' => '𖹌',
+  '𖹭' => '𖹍',
+  '𖹮' => '𖹎',
+  '𖹯' => '𖹏',
+  '𖹰' => '𖹐',
+  '𖹱' => '𖹑',
+  '𖹲' => '𖹒',
+  '𖹳' => '𖹓',
+  '𖹴' => '𖹔',
+  '𖹵' => '𖹕',
+  '𖹶' => '𖹖',
+  '𖹷' => '𖹗',
+  '𖹸' => '𖹘',
+  '𖹹' => '𖹙',
+  '𖹺' => '𖹚',
+  '𖹻' => '𖹛',
+  '𖹼' => '𖹜',
+  '𖹽' => '𖹝',
+  '𖹾' => '𖹞',
+  '𖹿' => '𖹟',
+  '𞤢' => '𞤀',
+  '𞤣' => '𞤁',
+  '𞤤' => '𞤂',
+  '𞤥' => '𞤃',
+  '𞤦' => '𞤄',
+  '𞤧' => '𞤅',
+  '𞤨' => '𞤆',
+  '𞤩' => '𞤇',
+  '𞤪' => '𞤈',
+  '𞤫' => '𞤉',
+  '𞤬' => '𞤊',
+  '𞤭' => '𞤋',
+  '𞤮' => '𞤌',
+  '𞤯' => '𞤍',
+  '𞤰' => '𞤎',
+  '𞤱' => '𞤏',
+  '𞤲' => '𞤐',
+  '𞤳' => '𞤑',
+  '𞤴' => '𞤒',
+  '𞤵' => '𞤓',
+  '𞤶' => '𞤔',
+  '𞤷' => '𞤕',
+  '𞤸' => '𞤖',
+  '𞤹' => '𞤗',
+  '𞤺' => '𞤘',
+  '𞤻' => '𞤙',
+  '𞤼' => '𞤚',
+  '𞤽' => '𞤛',
+  '𞤾' => '𞤜',
+  '𞤿' => '𞤝',
+  '𞥀' => '𞤞',
+  '𞥁' => '𞤟',
+  '𞥂' => '𞤠',
+  '𞥃' => '𞤡',
+  'ß' => 'SS',
+  'ff' => 'FF',
+  'fi' => 'FI',
+  'fl' => 'FL',
+  'ffi' => 'FFI',
+  'ffl' => 'FFL',
+  'ſt' => 'ST',
+  'st' => 'ST',
+  'և' => 'ԵՒ',
+  'ﬓ' => 'ՄՆ',
+  'ﬔ' => 'ՄԵ',
+  'ﬕ' => 'ՄԻ',
+  'ﬖ' => 'ՎՆ',
+  'ﬗ' => 'ՄԽ',
+  'ʼn' => 'ʼN',
+  'ΐ' => 'Ϊ́',
+  'ΰ' => 'Ϋ́',
+  'ǰ' => 'J̌',
+  'ẖ' => 'H̱',
+  'ẗ' => 'T̈',
+  'ẘ' => 'W̊',
+  'ẙ' => 'Y̊',
+  'ẚ' => 'Aʾ',
+  'ὐ' => 'Υ̓',
+  'ὒ' => 'Υ̓̀',
+  'ὔ' => 'Υ̓́',
+  'ὖ' => 'Υ̓͂',
+  'ᾶ' => 'Α͂',
+  'ῆ' => 'Η͂',
+  'ῒ' => 'Ϊ̀',
+  'ΐ' => 'Ϊ́',
+  'ῖ' => 'Ι͂',
+  'ῗ' => 'Ϊ͂',
+  'ῢ' => 'Ϋ̀',
+  'ΰ' => 'Ϋ́',
+  'ῤ' => 'Ρ̓',
+  'ῦ' => 'Υ͂',
+  'ῧ' => 'Ϋ͂',
+  'ῶ' => 'Ω͂',
+  'ᾈ' => 'ἈΙ',
+  'ᾉ' => 'ἉΙ',
+  'ᾊ' => 'ἊΙ',
+  'ᾋ' => 'ἋΙ',
+  'ᾌ' => 'ἌΙ',
+  'ᾍ' => 'ἍΙ',
+  'ᾎ' => 'ἎΙ',
+  'ᾏ' => 'ἏΙ',
+  'ᾘ' => 'ἨΙ',
+  'ᾙ' => 'ἩΙ',
+  'ᾚ' => 'ἪΙ',
+  'ᾛ' => 'ἫΙ',
+  'ᾜ' => 'ἬΙ',
+  'ᾝ' => 'ἭΙ',
+  'ᾞ' => 'ἮΙ',
+  'ᾟ' => 'ἯΙ',
+  'ᾨ' => 'ὨΙ',
+  'ᾩ' => 'ὩΙ',
+  'ᾪ' => 'ὪΙ',
+  'ᾫ' => 'ὫΙ',
+  'ᾬ' => 'ὬΙ',
+  'ᾭ' => 'ὭΙ',
+  'ᾮ' => 'ὮΙ',
+  'ᾯ' => 'ὯΙ',
+  'ᾼ' => 'ΑΙ',
+  'ῌ' => 'ΗΙ',
+  'ῼ' => 'ΩΙ',
+  'ᾲ' => 'ᾺΙ',
+  'ᾴ' => 'ΆΙ',
+  'ῂ' => 'ῊΙ',
+  'ῄ' => 'ΉΙ',
+  'ῲ' => 'ῺΙ',
+  'ῴ' => 'ΏΙ',
+  'ᾷ' => 'Α͂Ι',
+  'ῇ' => 'Η͂Ι',
+  'ῷ' => 'Ω͂Ι',
 );
diff --git a/bootstrap.php b/bootstrap.php
index 204a41b..1fedd1f 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -11,52 +11,137 @@
 
 use Symfony\Polyfill\Mbstring as p;
 
-if (!function_exists('mb_strlen')) {
-    define('MB_CASE_UPPER', 0);
-    define('MB_CASE_LOWER', 1);
-    define('MB_CASE_TITLE', 2);
+if (\PHP_VERSION_ID >= 80000) {
+    return require __DIR__.'/bootstrap80.php';
+}
 
-    function mb_convert_encoding($s, $to, $from = null) { return p\Mbstring::mb_convert_encoding($s, $to, $from); }
-    function mb_decode_mimeheader($s) { return p\Mbstring::mb_decode_mimeheader($s); }
-    function mb_encode_mimeheader($s, $charset = null, $transferEnc = null, $lf = null, $indent = null) { return p\Mbstring::mb_encode_mimeheader($s, $charset, $transferEnc, $lf, $indent); }
-    function mb_decode_numericentity($s, $convmap, $enc = null) { return p\Mbstring::mb_decode_numericentity($s, $convmap, $enc); }
-    function mb_encode_numericentity($s, $convmap, $enc = null, $is_hex = false) { return p\Mbstring::mb_encode_numericentity($s, $convmap, $enc, $is_hex); }
-    function mb_convert_case($s, $mode, $enc = null) { return p\Mbstring::mb_convert_case($s, $mode, $enc); }
-    function mb_internal_encoding($enc = null) { return p\Mbstring::mb_internal_encoding($enc); }
-    function mb_language($lang = null) { return p\Mbstring::mb_language($lang); }
+if (!function_exists('mb_convert_encoding')) {
+    function mb_convert_encoding($string, $to_encoding, $from_encoding = null) { return p\Mbstring::mb_convert_encoding($string, $to_encoding, $from_encoding); }
+}
+if (!function_exists('mb_decode_mimeheader')) {
+    function mb_decode_mimeheader($string) { return p\Mbstring::mb_decode_mimeheader($string); }
+}
+if (!function_exists('mb_encode_mimeheader')) {
+    function mb_encode_mimeheader($string, $charset = null, $transfer_encoding = null, $newline = "\r\n", $indent = 0) { return p\Mbstring::mb_encode_mimeheader($string, $charset, $transfer_encoding, $newline, $indent); }
+}
+if (!function_exists('mb_decode_numericentity')) {
+    function mb_decode_numericentity($string, $map, $encoding = null) { return p\Mbstring::mb_decode_numericentity($string, $map, $encoding); }
+}
+if (!function_exists('mb_encode_numericentity')) {
+    function mb_encode_numericentity($string, $map, $encoding = null, $hex = false) { return p\Mbstring::mb_encode_numericentity($string, $map, $encoding, $hex); }
+}
+if (!function_exists('mb_convert_case')) {
+    function mb_convert_case($string, $mode, $encoding = null) { return p\Mbstring::mb_convert_case($string, $mode, $encoding); }
+}
+if (!function_exists('mb_internal_encoding')) {
+    function mb_internal_encoding($encoding = null) { return p\Mbstring::mb_internal_encoding($encoding); }
+}
+if (!function_exists('mb_language')) {
+    function mb_language($language = null) { return p\Mbstring::mb_language($language); }
+}
+if (!function_exists('mb_list_encodings')) {
     function mb_list_encodings() { return p\Mbstring::mb_list_encodings(); }
+}
+if (!function_exists('mb_encoding_aliases')) {
     function mb_encoding_aliases($encoding) { return p\Mbstring::mb_encoding_aliases($encoding); }
-    function mb_check_encoding($var = null, $encoding = null) { return p\Mbstring::mb_check_encoding($var, $encoding); }
-    function mb_detect_encoding($str, $encodingList = null, $strict = false) { return p\Mbstring::mb_detect_encoding($str, $encodingList, $strict); }
-    function mb_detect_order($encodingList = null) { return p\Mbstring::mb_detect_order($encodingList); }
-    function mb_parse_str($s, &$result = array()) { parse_str($s, $result); }
-    function mb_strlen($s, $enc = null) { return p\Mbstring::mb_strlen($s, $enc); }
-    function mb_strpos($s, $needle, $offset = 0, $enc = null) { return p\Mbstring::mb_strpos($s, $needle, $offset, $enc); }
-    function mb_strtolower($s, $enc = null) { return p\Mbstring::mb_strtolower($s, $enc); }
-    function mb_strtoupper($s, $enc = null) { return p\Mbstring::mb_strtoupper($s, $enc); }
-    function mb_substitute_character($char = null) { return p\Mbstring::mb_substitute_character($char); }
-    function mb_substr($s, $start, $length = 2147483647, $enc = null) { return p\Mbstring::mb_substr($s, $start, $length, $enc); }
-    function mb_stripos($s, $needle, $offset = 0, $enc = null) { return p\Mbstring::mb_stripos($s, $needle, $offset, $enc); }
-    function mb_stristr($s, $needle, $part = false, $enc = null) { return p\Mbstring::mb_stristr($s, $needle, $part, $enc); }
-    function mb_strrchr($s, $needle, $part = false, $enc = null) { return p\Mbstring::mb_strrchr($s, $needle, $part, $enc); }
-    function mb_strrichr($s, $needle, $part = false, $enc = null) { return p\Mbstring::mb_strrichr($s, $needle, $part, $enc); }
-    function mb_strripos($s, $needle, $offset = 0, $enc = null) { return p\Mbstring::mb_strripos($s, $needle, $offset, $enc); }
-    function mb_strrpos($s, $needle, $offset = 0, $enc = null) { return p\Mbstring::mb_strrpos($s, $needle, $offset, $enc); }
-    function mb_strstr($s, $needle, $part = false, $enc = null) { return p\Mbstring::mb_strstr($s, $needle, $part, $enc); }
+}
+if (!function_exists('mb_check_encoding')) {
+    function mb_check_encoding($value = null, $encoding = null) { return p\Mbstring::mb_check_encoding($value, $encoding); }
+}
+if (!function_exists('mb_detect_encoding')) {
+    function mb_detect_encoding($string, $encodings = null, $strict = false) { return p\Mbstring::mb_detect_encoding($string, $encodings, $strict); }
+}
+if (!function_exists('mb_detect_order')) {
+    function mb_detect_order($encoding = null) { return p\Mbstring::mb_detect_order($encoding); }
+}
+if (!function_exists('mb_parse_str')) {
+    function mb_parse_str($string, &$result = []) { parse_str($string, $result); return (bool) $result; }
+}
+if (!function_exists('mb_strlen')) {
+    function mb_strlen($string, $encoding = null) { return p\Mbstring::mb_strlen($string, $encoding); }
+}
+if (!function_exists('mb_strpos')) {
+    function mb_strpos($haystack, $needle, $offset = 0, $encoding = null) { return p\Mbstring::mb_strpos($haystack, $needle, $offset, $encoding); }
+}
+if (!function_exists('mb_strtolower')) {
+    function mb_strtolower($string, $encoding = null) { return p\Mbstring::mb_strtolower($string, $encoding); }
+}
+if (!function_exists('mb_strtoupper')) {
+    function mb_strtoupper($string, $encoding = null) { return p\Mbstring::mb_strtoupper($string, $encoding); }
+}
+if (!function_exists('mb_substitute_character')) {
+    function mb_substitute_character($substitute_character = null) { return p\Mbstring::mb_substitute_character($substitute_character); }
+}
+if (!function_exists('mb_substr')) {
+    function mb_substr($string, $start, $length = 2147483647, $encoding = null) { return p\Mbstring::mb_substr($string, $start, $length, $encoding); }
+}
+if (!function_exists('mb_stripos')) {
+    function mb_stripos($haystack, $needle, $offset = 0, $encoding = null) { return p\Mbstring::mb_stripos($haystack, $needle, $offset, $encoding); }
+}
+if (!function_exists('mb_stristr')) {
+    function mb_stristr($haystack, $needle, $before_needle = false, $encoding = null) { return p\Mbstring::mb_stristr($haystack, $needle, $before_needle, $encoding); }
+}
+if (!function_exists('mb_strrchr')) {
+    function mb_strrchr($haystack, $needle, $before_needle = false, $encoding = null) { return p\Mbstring::mb_strrchr($haystack, $needle, $before_needle, $encoding); }
+}
+if (!function_exists('mb_strrichr')) {
+    function mb_strrichr($haystack, $needle, $before_needle = false, $encoding = null) { return p\Mbstring::mb_strrichr($haystack, $needle, $before_needle, $encoding); }
+}
+if (!function_exists('mb_strripos')) {
+    function mb_strripos($haystack, $needle, $offset = 0, $encoding = null) { return p\Mbstring::mb_strripos($haystack, $needle, $offset, $encoding); }
+}
+if (!function_exists('mb_strrpos')) {
+    function mb_strrpos($haystack, $needle, $offset = 0, $encoding = null) { return p\Mbstring::mb_strrpos($haystack, $needle, $offset, $encoding); }
+}
+if (!function_exists('mb_strstr')) {
+    function mb_strstr($haystack, $needle, $before_needle = false, $encoding = null) { return p\Mbstring::mb_strstr($haystack, $needle, $before_needle, $encoding); }
+}
+if (!function_exists('mb_get_info')) {
     function mb_get_info($type = 'all') { return p\Mbstring::mb_get_info($type); }
-    function mb_http_output($enc = null) { return p\Mbstring::mb_http_output($enc); }
-    function mb_strwidth($s, $enc = null) { return p\Mbstring::mb_strwidth($s, $enc); }
-    function mb_substr_count($haystack, $needle, $enc = null) { return p\Mbstring::mb_substr_count($haystack, $needle, $enc); }
-    function mb_output_handler($contents, $status) { return p\Mbstring::mb_output_handler($contents, $status); }
-    function mb_http_input($type = '') { return p\Mbstring::mb_http_input($type); }
-    function mb_convert_variables($toEncoding, $fromEncoding, &$a = null, &$b = null, &$c = null, &$d = null, &$e = null, &$f = null) { return p\Mbstring::mb_convert_variables($toEncoding, $fromEncoding, $a, $b, $c, $d, $e, $f); }
 }
-if (!function_exists('mb_chr')) {
-    function mb_ord($s, $enc = null) { return p\Mbstring::mb_ord($s, $enc); }
-    function mb_chr($code, $enc = null) { return p\Mbstring::mb_chr($code, $enc); }
-    function mb_scrub($s, $enc = null) { $enc = null === $enc ? mb_internal_encoding() : $enc; return mb_convert_encoding($s, $enc, $enc); }
+if (!function_exists('mb_http_output')) {
+    function mb_http_output($encoding = null) { return p\Mbstring::mb_http_output($encoding); }
+}
+if (!function_exists('mb_strwidth')) {
+    function mb_strwidth($string, $encoding = null) { return p\Mbstring::mb_strwidth($string, $encoding); }
+}
+if (!function_exists('mb_substr_count')) {
+    function mb_substr_count($haystack, $needle, $encoding = null) { return p\Mbstring::mb_substr_count($haystack, $needle, $encoding); }
+}
+if (!function_exists('mb_output_handler')) {
+    function mb_output_handler($string, $status) { return p\Mbstring::mb_output_handler($string, $status); }
+}
+if (!function_exists('mb_http_input')) {
+    function mb_http_input($type = null) { return p\Mbstring::mb_http_input($type); }
+}
+
+if (!function_exists('mb_convert_variables')) {
+    function mb_convert_variables($to_encoding, $from_encoding, &...$vars) { return p\Mbstring::mb_convert_variables($to_encoding, $from_encoding, ...$vars); }
 }
 
+if (!function_exists('mb_ord')) {
+    function mb_ord($string, $encoding = null) { return p\Mbstring::mb_ord($string, $encoding); }
+}
+if (!function_exists('mb_chr')) {
+    function mb_chr($codepoint, $encoding = null) { return p\Mbstring::mb_chr($codepoint, $encoding); }
+}
+if (!function_exists('mb_scrub')) {
+    function mb_scrub($string, $encoding = null) { $encoding = null === $encoding ? mb_internal_encoding() : $encoding; return mb_convert_encoding($string, $encoding, $encoding); }
+}
 if (!function_exists('mb_str_split')) {
-    function mb_str_split($string, $split_length = 1, $encoding = null) { return p\Mbstring::mb_str_split($string, $split_length, $encoding); }
+    function mb_str_split($string, $length = 1, $encoding = null) { return p\Mbstring::mb_str_split($string, $length, $encoding); }
+}
+
+if (extension_loaded('mbstring')) {
+    return;
+}
+
+if (!defined('MB_CASE_UPPER')) {
+    define('MB_CASE_UPPER', 0);
+}
+if (!defined('MB_CASE_LOWER')) {
+    define('MB_CASE_LOWER', 1);
+}
+if (!defined('MB_CASE_TITLE')) {
+    define('MB_CASE_TITLE', 2);
 }
diff --git a/bootstrap80.php b/bootstrap80.php
new file mode 100644
index 0000000..82f5ac4
--- /dev/null
+++ b/bootstrap80.php
@@ -0,0 +1,143 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Symfony\Polyfill\Mbstring as p;
+
+if (!function_exists('mb_convert_encoding')) {
+    function mb_convert_encoding(array|string|null $string, ?string $to_encoding, array|string|null $from_encoding = null): array|string|false { return p\Mbstring::mb_convert_encoding($string ?? '', (string) $to_encoding, $from_encoding); }
+}
+if (!function_exists('mb_decode_mimeheader')) {
+    function mb_decode_mimeheader(?string $string): string { return p\Mbstring::mb_decode_mimeheader((string) $string); }
+}
+if (!function_exists('mb_encode_mimeheader')) {
+    function mb_encode_mimeheader(?string $string, ?string $charset = null, ?string $transfer_encoding = null, ?string $newline = "\r\n", ?int $indent = 0): string { return p\Mbstring::mb_encode_mimeheader((string) $string, $charset, $transfer_encoding, (string) $newline, (int) $indent); }
+}
+if (!function_exists('mb_decode_numericentity')) {
+    function mb_decode_numericentity(?string $string, array $map, ?string $encoding = null): string { return p\Mbstring::mb_decode_numericentity((string) $string, $map, $encoding); }
+}
+if (!function_exists('mb_encode_numericentity')) {
+    function mb_encode_numericentity(?string $string, array $map, ?string $encoding = null, ?bool $hex = false): string { return p\Mbstring::mb_encode_numericentity((string) $string, $map, $encoding, (bool) $hex); }
+}
+if (!function_exists('mb_convert_case')) {
+    function mb_convert_case(?string $string, ?int $mode, ?string $encoding = null): string { return p\Mbstring::mb_convert_case((string) $string, (int) $mode, $encoding); }
+}
+if (!function_exists('mb_internal_encoding')) {
+    function mb_internal_encoding(?string $encoding = null): string|bool { return p\Mbstring::mb_internal_encoding($encoding); }
+}
+if (!function_exists('mb_language')) {
+    function mb_language(?string $language = null): string|bool { return p\Mbstring::mb_language($language); }
+}
+if (!function_exists('mb_list_encodings')) {
+    function mb_list_encodings(): array { return p\Mbstring::mb_list_encodings(); }
+}
+if (!function_exists('mb_encoding_aliases')) {
+    function mb_encoding_aliases(?string $encoding): array { return p\Mbstring::mb_encoding_aliases((string) $encoding); }
+}
+if (!function_exists('mb_check_encoding')) {
+    function mb_check_encoding(array|string|null $value = null, ?string $encoding = null): bool { return p\Mbstring::mb_check_encoding($value, $encoding); }
+}
+if (!function_exists('mb_detect_encoding')) {
+    function mb_detect_encoding(?string $string, array|string|null $encodings = null, ?bool $strict = false): string|false { return p\Mbstring::mb_detect_encoding((string) $string, $encodings, (bool) $strict); }
+}
+if (!function_exists('mb_detect_order')) {
+    function mb_detect_order(array|string|null $encoding = null): array|bool { return p\Mbstring::mb_detect_order($encoding); }
+}
+if (!function_exists('mb_parse_str')) {
+    function mb_parse_str(?string $string, &$result = []): bool { parse_str((string) $string, $result); return (bool) $result; }
+}
+if (!function_exists('mb_strlen')) {
+    function mb_strlen(?string $string, ?string $encoding = null): int { return p\Mbstring::mb_strlen((string) $string, $encoding); }
+}
+if (!function_exists('mb_strpos')) {
+    function mb_strpos(?string $haystack, ?string $needle, ?int $offset = 0, ?string $encoding = null): int|false { return p\Mbstring::mb_strpos((string) $haystack, (string) $needle, (int) $offset, $encoding); }
+}
+if (!function_exists('mb_strtolower')) {
+    function mb_strtolower(?string $string, ?string $encoding = null): string { return p\Mbstring::mb_strtolower((string) $string, $encoding); }
+}
+if (!function_exists('mb_strtoupper')) {
+    function mb_strtoupper(?string $string, ?string $encoding = null): string { return p\Mbstring::mb_strtoupper((string) $string, $encoding); }
+}
+if (!function_exists('mb_substitute_character')) {
+    function mb_substitute_character(string|int|null $substitute_character = null): string|int|bool { return p\Mbstring::mb_substitute_character($substitute_character); }
+}
+if (!function_exists('mb_substr')) {
+    function mb_substr(?string $string, ?int $start, ?int $length = null, ?string $encoding = null): string { return p\Mbstring::mb_substr((string) $string, (int) $start, $length, $encoding); }
+}
+if (!function_exists('mb_stripos')) {
+    function mb_stripos(?string $haystack, ?string $needle, ?int $offset = 0, ?string $encoding = null): int|false { return p\Mbstring::mb_stripos((string) $haystack, (string) $needle, (int) $offset, $encoding); }
+}
+if (!function_exists('mb_stristr')) {
+    function mb_stristr(?string $haystack, ?string $needle, ?bool $before_needle = false, ?string $encoding = null): string|false { return p\Mbstring::mb_stristr((string) $haystack, (string) $needle, (bool) $before_needle, $encoding); }
+}
+if (!function_exists('mb_strrchr')) {
+    function mb_strrchr(?string $haystack, ?string $needle, ?bool $before_needle = false, ?string $encoding = null): string|false { return p\Mbstring::mb_strrchr((string) $haystack, (string) $needle, (bool) $before_needle, $encoding); }
+}
+if (!function_exists('mb_strrichr')) {
+    function mb_strrichr(?string $haystack, ?string $needle, ?bool $before_needle = false, ?string $encoding = null): string|false { return p\Mbstring::mb_strrichr((string) $haystack, (string) $needle, (bool) $before_needle, $encoding); }
+}
+if (!function_exists('mb_strripos')) {
+    function mb_strripos(?string $haystack, ?string $needle, ?int $offset = 0, ?string $encoding = null): int|false { return p\Mbstring::mb_strripos((string) $haystack, (string) $needle, (int) $offset, $encoding); }
+}
+if (!function_exists('mb_strrpos')) {
+    function mb_strrpos(?string $haystack, ?string $needle, ?int $offset = 0, ?string $encoding = null): int|false { return p\Mbstring::mb_strrpos((string) $haystack, (string) $needle, (int) $offset, $encoding); }
+}
+if (!function_exists('mb_strstr')) {
+    function mb_strstr(?string $haystack, ?string $needle, ?bool $before_needle = false, ?string $encoding = null): string|false { return p\Mbstring::mb_strstr((string) $haystack, (string) $needle, (bool) $before_needle, $encoding); }
+}
+if (!function_exists('mb_get_info')) {
+    function mb_get_info(?string $type = 'all'): array|string|int|false { return p\Mbstring::mb_get_info((string) $type); }
+}
+if (!function_exists('mb_http_output')) {
+    function mb_http_output(?string $encoding = null): string|bool { return p\Mbstring::mb_http_output($encoding); }
+}
+if (!function_exists('mb_strwidth')) {
+    function mb_strwidth(?string $string, ?string $encoding = null): int { return p\Mbstring::mb_strwidth((string) $string, $encoding); }
+}
+if (!function_exists('mb_substr_count')) {
+    function mb_substr_count(?string $haystack, ?string $needle, ?string $encoding = null): int { return p\Mbstring::mb_substr_count((string) $haystack, (string) $needle, $encoding); }
+}
+if (!function_exists('mb_output_handler')) {
+    function mb_output_handler(?string $string, ?int $status): string { return p\Mbstring::mb_output_handler((string) $string, (int) $status); }
+}
+if (!function_exists('mb_http_input')) {
+    function mb_http_input(?string $type = null): array|string|false { return p\Mbstring::mb_http_input($type); }
+}
+
+if (!function_exists('mb_convert_variables')) {
+    function mb_convert_variables(?string $to_encoding, array|string|null $from_encoding, mixed &$var, mixed &...$vars): string|false { return p\Mbstring::mb_convert_variables((string) $to_encoding, $from_encoding ?? '', $var, ...$vars); }
+}
+
+if (!function_exists('mb_ord')) {
+    function mb_ord(?string $string, ?string $encoding = null): int|false { return p\Mbstring::mb_ord((string) $string, $encoding); }
+}
+if (!function_exists('mb_chr')) {
+    function mb_chr(?int $codepoint, ?string $encoding = null): string|false { return p\Mbstring::mb_chr((int) $codepoint, $encoding); }
+}
+if (!function_exists('mb_scrub')) {
+    function mb_scrub(?string $string, ?string $encoding = null): string { $encoding ??= mb_internal_encoding(); return mb_convert_encoding((string) $string, $encoding, $encoding); }
+}
+if (!function_exists('mb_str_split')) {
+    function mb_str_split(?string $string, ?int $length = 1, ?string $encoding = null): array { return p\Mbstring::mb_str_split((string) $string, (int) $length, $encoding); }
+}
+
+if (extension_loaded('mbstring')) {
+    return;
+}
+
+if (!defined('MB_CASE_UPPER')) {
+    define('MB_CASE_UPPER', 0);
+}
+if (!defined('MB_CASE_LOWER')) {
+    define('MB_CASE_LOWER', 1);
+}
+if (!defined('MB_CASE_TITLE')) {
+    define('MB_CASE_TITLE', 2);
+}
diff --git a/composer.json b/composer.json
index 308f009..9cd2e92 100644
--- a/composer.json
+++ b/composer.json
@@ -16,7 +16,10 @@
         }
     ],
     "require": {
-        "php": ">=5.3.3"
+        "php": ">=7.1"
+    },
+    "provide": {
+        "ext-mbstring": "*"
     },
     "autoload": {
         "psr-4": { "Symfony\\Polyfill\\Mbstring\\": "" },
@@ -28,7 +31,11 @@
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {
-            "dev-master": "1.12-dev"
+            "dev-main": "1.26-dev"
+        },
+        "thanks": {
+            "name": "symfony/polyfill",
+            "url": "https://github.com/symfony/polyfill"
         }
     }
 }