* WordPress implementation for PHP functions either missing from older PHP versions or not included by default.
// If gettext isn't available.
if ( ! function_exists( '_' ) ) {
* Returns whether PCRE/u (PCRE_UTF8 modifier) is available for use.
* @param bool $set - Used for testing only
* null : default - get PCRE/u capability
* false : Used for testing - return false for future calls to this function
* 'reset': Used for testing - restore default behavior of this function
function _wp_can_use_pcre_u( $set = null ) {
static $utf8_pcre = 'reset';
if ( 'reset' === $utf8_pcre ) {
// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged -- intentional error generated to detect PCRE/u support.
$utf8_pcre = @preg_match( '/^./u', 'a' );
* Indicates if a given slug for a character set represents the UTF-8 text encoding.
* A charset is considered to represent UTF-8 if it is a case-insensitive match
* of "UTF-8" with or without the hyphen.
* true === _is_utf8_charset( 'UTF-8' );
* true === _is_utf8_charset( 'utf8' );
* false === _is_utf8_charset( 'latin1' );
* false === _is_utf8_charset( 'UTF 8' );
* false === _is_utf8_charset( [ 'charset' => 'utf-8' ] );
* `is_utf8_charset` should be used outside of this file.
* @param string $charset_slug Slug representing a text character encoding, or "charset".
* E.g. "UTF-8", "Windows-1252", "ISO-8859-1", "SJIS".
* @return bool Whether the slug represents the UTF-8 encoding.
function _is_utf8_charset( $charset_slug ) {
if ( ! is_string( $charset_slug ) ) {
0 === strcasecmp( 'UTF-8', $charset_slug ) ||
0 === strcasecmp( 'UTF8', $charset_slug )
if ( ! function_exists( 'mb_substr' ) ) :
* Compat function to mimic mb_substr().
* @param string $string The string to extract the substring from.
* @param int $start Position to being extraction from in `$string`.
* @param int|null $length Optional. Maximum number of characters to extract from `$string`.
* @param string|null $encoding Optional. Character encoding to use. Default null.
* @return string Extracted substring.
function mb_substr( $string, $start, $length = null, $encoding = null ) { // phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.stringFound
return _mb_substr( $string, $start, $length, $encoding );
* Internal compat function to mimic mb_substr().
* Only understands UTF-8 and 8bit. All other character sets will be treated as 8bit.
* For `$encoding === UTF-8`, the `$str` input is expected to be a valid UTF-8 byte
* sequence. The behavior of this function for invalid inputs is undefined.
* @param string $str The string to extract the substring from.
* @param int $start Position to being extraction from in `$str`.
* @param int|null $length Optional. Maximum number of characters to extract from `$str`.
* @param string|null $encoding Optional. Character encoding to use. Default null.
* @return string Extracted substring.
function _mb_substr( $str, $start, $length = null, $encoding = null ) {
if ( null === $encoding ) {
$encoding = get_option( 'blog_charset' );
* The solution below works only for UTF-8, so in case of a different
* charset just use built-in substr().
if ( ! _is_utf8_charset( $encoding ) ) {
return is_null( $length ) ? substr( $str, $start ) : substr( $str, $start, $length );
if ( _wp_can_use_pcre_u() ) {
// Use the regex unicode support to separate the UTF-8 characters into an array.
preg_match_all( '/./us', $str, $match );
$chars = is_null( $length ) ? array_slice( $match[0], $start ) : array_slice( $match[0], $start, $length );
return implode( '', $chars );
[\x00-\x7F] # single-byte sequences 0xxxxxxx
| [\xC2-\xDF][\x80-\xBF] # double-byte sequences 110xxxxx 10xxxxxx
| \xE0[\xA0-\xBF][\x80-\xBF] # triple-byte sequences 1110xxxx 10xxxxxx * 2
| [\xE1-\xEC][\x80-\xBF]{2}
| \xED[\x80-\x9F][\x80-\xBF]
| [\xEE-\xEF][\x80-\xBF]{2}
| \xF0[\x90-\xBF][\x80-\xBF]{2} # four-byte sequences 11110xxx 10xxxxxx * 3
| [\xF1-\xF3][\x80-\xBF]{3}
| \xF4[\x80-\x8F][\x80-\xBF]{2}
// Start with 1 element instead of 0 since the first thing we do is pop.
// We had some string left over from the last round, but we counted it in that last round.
* Split by UTF-8 character, limit to 1000 characters (last array element will contain
* the rest of the string).
$pieces = preg_split( $regex, $str, 1000, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY );
$chars = array_merge( $chars, $pieces );
// If there's anything left over, repeat the loop.
} while ( count( $pieces ) > 1 && $str = array_pop( $pieces ) );
return implode( '', array_slice( $chars, $start, $length ) );
if ( ! function_exists( 'mb_strlen' ) ) :
* Compat function to mimic mb_strlen().
* @param string $string The string to retrieve the character length from.
* @param string|null $encoding Optional. Character encoding to use. Default null.
* @return int String length of `$string`.
function mb_strlen( $string, $encoding = null ) { // phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.stringFound
return _mb_strlen( $string, $encoding );
* Internal compat function to mimic mb_strlen().
* Only understands UTF-8 and 8bit. All other character sets will be treated as 8bit.
* For `$encoding === UTF-8`, the `$str` input is expected to be a valid UTF-8 byte
* sequence. The behavior of this function for invalid inputs is undefined.
* @param string $str The string to retrieve the character length from.
* @param string|null $encoding Optional. Character encoding to use. Default null.
* @return int String length of `$str`.
function _mb_strlen( $str, $encoding = null ) {
if ( null === $encoding ) {
$encoding = get_option( 'blog_charset' );
* The solution below works only for UTF-8, so in case of a different charset
* just use built-in strlen().
if ( ! _is_utf8_charset( $encoding ) ) {
if ( _wp_can_use_pcre_u() ) {
// Use the regex unicode support to separate the UTF-8 characters into an array.
preg_match_all( '/./us', $str, $match );
return count( $match[0] );
[\x00-\x7F] # single-byte sequences 0xxxxxxx
| [\xC2-\xDF][\x80-\xBF] # double-byte sequences 110xxxxx 10xxxxxx
| \xE0[\xA0-\xBF][\x80-\xBF] # triple-byte sequences 1110xxxx 10xxxxxx * 2
| [\xE1-\xEC][\x80-\xBF]{2}
| \xED[\x80-\x9F][\x80-\xBF]
| [\xEE-\xEF][\x80-\xBF]{2}
| \xF0[\x90-\xBF][\x80-\xBF]{2} # four-byte sequences 11110xxx 10xxxxxx * 3
| [\xF1-\xF3][\x80-\xBF]{3}
| \xF4[\x80-\x8F][\x80-\xBF]{2}
// Start at 1 instead of 0 since the first thing we do is decrement.
// We had some string left over from the last round, but we counted it in that last round.
* Split by UTF-8 character, limit to 1000 characters (last array element will contain
* the rest of the string).
$pieces = preg_split( $regex, $str, 1000 );
$count += count( $pieces );
// If there's anything left over, repeat the loop.
} while ( $str = array_pop( $pieces ) );
// Fencepost: preg_split() always returns one extra item in the array.
if ( ! function_exists( 'hash_hmac' ) ) :
* Compat function to mimic hash_hmac().
* The Hash extension is bundled with PHP by default since PHP 5.1.2.
* However, the extension may be explicitly disabled on select servers.
* As of PHP 7.4.0, the Hash extension is a core PHP extension and can no
* I.e. when PHP 7.4.0 becomes the minimum requirement, this polyfill
* and the associated `_hash_hmac()` function can be safely removed.
* @param string $algo Hash algorithm. Accepts 'md5' or 'sha1'.
* @param string $data Data to be hashed.
* @param string $key Secret key to use for generating the hash.
* @param bool $binary Optional. Whether to output raw binary data (true),
* or lowercase hexits (false). Default false.
* @return string|false The hash in output determined by `$binary`.
* False if `$algo` is unknown or invalid.
function hash_hmac( $algo, $data, $key, $binary = false ) {
return _hash_hmac( $algo, $data, $key, $binary );
* Internal compat function to mimic hash_hmac().
* @param string $algo Hash algorithm. Accepts 'md5' or 'sha1'.
* @param string $data Data to be hashed.
* @param string $key Secret key to use for generating the hash.
* @param bool $binary Optional. Whether to output raw binary data (true),
* or lowercase hexits (false). Default false.
* @return string|false The hash in output determined by `$binary`.
* False if `$algo` is unknown or invalid.
function _hash_hmac( $algo, $data, $key, $binary = false ) {
if ( ! isset( $packs[ $algo ] ) ) {
if ( strlen( $key ) > 64 ) {
$key = pack( $pack, $algo( $key ) );
$key = str_pad( $key, 64, chr( 0 ) );
$ipad = ( substr( $key, 0, 64 ) ^ str_repeat( chr( 0x36 ), 64 ) );
$opad = ( substr( $key, 0, 64 ) ^ str_repeat( chr( 0x5C ), 64 ) );
$hmac = $algo( $opad . pack( $pack, $algo( $ipad . $data ) ) );
return pack( $pack, $hmac );
if ( ! function_exists( 'hash_equals' ) ) :
* Timing attack safe string comparison.
* Compares two strings using the same time whether they're equal or not.
* Note: It can leak the length of a string when arguments of differing length are supplied.
* This function was added in PHP 5.6.
* However, the Hash extension may be explicitly disabled on select servers.
* As of PHP 7.4.0, the Hash extension is a core PHP extension and can no
* I.e. when PHP 7.4.0 becomes the minimum requirement, this polyfill
* @param string $known_string Expected string.
* @param string $user_string Actual, user supplied, string.
* @return bool Whether strings are equal.
function hash_equals( $known_string, $user_string ) {
$known_string_length = strlen( $known_string );
if ( strlen( $user_string ) !== $known_string_length ) {
// Do not attempt to "optimize" this.
for ( $i = 0; $i < $known_string_length; $i++ ) {
$result |= ord( $known_string[ $i ] ) ^ ord( $user_string[ $i ] );
// sodium_crypto_box() was introduced in PHP 7.2.
if ( ! function_exists( 'sodium_crypto_box' ) ) {
require ABSPATH . WPINC . '/sodium_compat/autoload.php';
if ( ! function_exists( 'is_countable' ) ) {
* Polyfill for is_countable() function added in PHP 7.3.
* Verify that the content of a variable is an array or an object
* implementing the Countable interface.
* @param mixed $value The value to check.
* @return bool True if `$value` is countable, false otherwise.
function is_countable( $value ) {
return ( is_array( $value )
|| $value instanceof Countable
|| $value instanceof SimpleXMLElement
|| $value instanceof ResourceBundle
if ( ! function_exists( 'array_key_first' ) ) {
* Polyfill for array_key_first() function added in PHP 7.3.
* Get the first key of the given array without affecting
* the internal array pointer.
* @param array $array An array.
* @return string|int|null The first key of array if the array
* is not empty; `null` otherwise.
function array_key_first( array $array ) { // phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.arrayFound
foreach ( $array as $key => $value ) {
if ( ! function_exists( 'array_key_last' ) ) {
* Polyfill for `array_key_last()` function added in PHP 7.3.
* Get the last key of the given array without affecting the
* internal array pointer.
* @param array $array An array.
* @return string|int|null The last key of array if the array
*. is not empty; `null` otherwise.
function array_key_last( array $array ) { // phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.arrayFound
if ( ! function_exists( 'array_is_list' ) ) {
* Polyfill for `array_is_list()` function added in PHP 8.1.
* Determines if the given array is a list.
* An array is considered a list if its keys consist of consecutive numbers from 0 to count($array)-1.
* @see https://github.com/symfony/polyfill-php81/tree/main
* @param array<mixed> $arr The array being evaluated.
* @return bool True if array is a list, false otherwise.
function array_is_list( $arr ) {
if ( ( array() === $arr ) || ( array_values( $arr ) === $arr ) ) {
foreach ( $arr as $k => $v ) {
if ( ++$next_key !== $k ) {
if ( ! function_exists( 'str_contains' ) ) {
* Polyfill for `str_contains()` function added in PHP 8.0.
* Performs a case-sensitive check indicating if needle is
* @param string $haystack The string to search in.
* @param string $needle The substring to search for in the `$haystack`.
* @return bool True if `$needle` is in `$haystack`, otherwise false.
function str_contains( $haystack, $needle ) {
return false !== strpos( $haystack, $needle );
if ( ! function_exists( 'str_starts_with' ) ) {
* Polyfill for `str_starts_with()` function added in PHP 8.0.
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
