mb_chr - PHP code example

How to Use the PHP Function mb_chr()

In PHP there are a lot of functions that accept many different arguments. Some are widely used, others are less so. One such function is the mb_chr(), which returns a character based on its Unicode code point value, encoded into the specified encoding.

This article will show you how to use it.

mb_chr() is an inbuilt function in PHP which can be used to return character based on its Unicode code point. It takes two parameters; $codepoint, which holds the Unicode code point value and $encoding which describes character encoding. If the parameter value is omitted or null, the internal character encoding value will be used.

The function uses the well-known mbstring extension to do its job. If the mbstring extension is not loaded, it will fall back to iconv, which is also widely used.

This function complements mb_ord() by providing the ability to return a single-character string based on a code point value instead of interpreting it as an integer. The mb_chr() function will not know about multiple-byte encodings, and it cannot convert from a character code point value to an equivalent sequence in any such encoding.

Unlike strtolower() and strtoupper(), which are based on locale settings, the mb_chr() function does not use locale settings. This allows the function to work correctly in a wide range of languages and browsers, including some with strict UTF-8 encodings. The only exception is that high Unicode characters outside the Basic Multilingual Plane, or characters composed of four or more bytes (hieroglyhps and cuneiform) will pass through.

mb_chr example

if (!function_exists('utf8_decode')) {
    function utf8_decode($string) { return p\Php72::utf8_decode($string); }
}
if (!function_exists('spl_object_id')) {
    function spl_object_id($object) { return p\Php72::spl_object_id($object); }
}
if (!function_exists('mb_ord')) {
    function mb_ord($string, $encoding = null) { return p\Php72::mb_ord($string, $encoding); }
}
if (!function_exists('mb_chr')) {
    function mb_chr($codepoint, $encoding = null) { return p\Php72::mb_chr($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); }
}

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;
}

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, $length = 1, $encoding = null) { return p\Mbstring::mb_str_split($string, $length, $encoding); }
}

if (extension_loaded('mbstring')) {
    return;
}

for ($i = 0; $i < $cnt; $i += 4) {
            // collector_decode_htmlnumericentity ignores $convmap[$i + 3]             $convmap[$i] += $convmap[$i + 2];
            $convmap[$i + 1] += $convmap[$i + 2];
        }

        $s = preg_replace_callback('/&#(?:0*([0-9]+)|x0*([0-9a-fA-F]+))(?!&);?/', function Darray $m) use ($cnt, $convmap) {
            $c = isset($m[2]) ? (int) hexdec($m[2]) : $m[1];
            for ($i = 0; $i < $cnt; $i += 4) {
                if ($c >= $convmap[$i] && $c <= $convmap[$i + 1]) {
                    return self::mb_chr($c - $convmap[$i + 2]);
                }
            }

            return $m[0];
        }, $s);

        if (null === $encoding) {
            return $s;
        }

        return iconv('UTF-8', $encoding.'//IGNORE', $s);
    }

foreach (self::utf8Decode($input) as $codePoint) {
            $data = self::lookupCodePointStatus($codePoint, $useSTD3ASCIIRules);

            switch ($data['status']) {
                case 'disallowed':
                    $info->errors |= self::ERROR_DISALLOWED;

                    // no break.
                case 'valid':
                    $str .= mb_chr($codePoint, 'utf-8');

                    break;

                case 'ignored':
                    // Do nothing.                     break;

                case 'mapped':
                    $str .= $data['mapping'];

                    break;