* WordPress implementation for PHP functions either missing from older PHP versions or not included by default.
* This file is loaded extremely early and the functions can be relied upon by drop-ins.
* Ergo, please ensure you do not rely on external functions when writing code for this file.
* Only use functions built into PHP or are defined in this file and have adequate testing
* and error suppression to ensure the file will run correctly and not break websites.
// If gettext isn't available.
if ( ! function_exists( '_' ) ) {
* Compat function to mimic _(), an alias of gettext().
* @see https://php.net/manual/en/function.gettext.php
* @param string $message The message being translated.
* Returns whether PCRE/u (PCRE_UTF8 modifier) is available for use.
* @since 6.9.0 Deprecated the `$set` argument.
* @param bool $set Deprecated. This argument is no longer used for testing purposes.
function _wp_can_use_pcre_u( $set = null ) {
static $utf8_pcre = null;
_deprecated_argument( __FUNCTION__, '6.9.0' );
if ( isset( $utf8_pcre ) ) {
function ( $errno, $errstr ) use ( &$utf8_pcre ) {
if ( str_starts_with( $errstr, 'preg_match():' ) ) {
* Attempt to compile a PCRE pattern with the PCRE_UTF8 flag. For
* systems lacking Unicode support this will trigger a warning
* during compilation, which the error handler will intercept.
* 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 supports UTF-8 and non-shifting single-byte encodings. For all other encodings
* expect the substrings to be misaligned. When the given encoding (or the `blog_charset`
* if none is provided) isn’t UTF-8 then the function returns the output of {@see \substr()}.
* @param string $str The string to extract the substring from.
* @param int $start Character offset at which to start the substring extraction.
* @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 ) {
// The solution below works only for UTF-8; treat all other encodings as byte streams.
if ( ! _is_utf8_charset( $encoding ?? get_option( 'blog_charset' ) ) ) {
return is_null( $length ) ? substr( $str, $start ) : substr( $str, $start, $length );
$total_length = ( $start < 0 || $length < 0 )
? _wp_utf8_codepoint_count( $str )
$normalized_start = $start < 0
? max( 0, $total_length + $start )
* The starting offset is provided as characters, which means this needs to
* find how many bytes that many characters occupies at the start of the string.
$starting_byte_offset = _wp_utf8_codepoint_span( $str, 0, $normalized_start );
$normalized_length = $length < 0
? max( 0, $total_length - $normalized_start + $length )
* This is the main step. It finds how many bytes the given length of code points
* occupies in the input, starting at the byte offset calculated above.
$byte_length = isset( $normalized_length )
? _wp_utf8_codepoint_span( $str, $starting_byte_offset, $normalized_length )
: ( strlen( $str ) - $starting_byte_offset );
// The result is a normal byte-level substring using the computed ranges.
return substr( $str, $starting_byte_offset, $byte_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 supports UTF-8 and non-shifting single-byte encodings. For all other
* encodings expect the counts to be wrong. When the given encoding (or the
* `blog_charset` if none is provided) isn’t UTF-8 then the function returns
* the byte-count of the provided string.
* @param string $str The string to retrieve the character length from.
* @param string|null $encoding Optional. Count characters according to this encoding.
* Default is to consult `blog_charset`.
* @return int Count of code points if UTF-8, byte length otherwise.
function _mb_strlen( $str, $encoding = null ) {
return _is_utf8_charset( $encoding ?? get_option( 'blog_charset' ) )
? _wp_utf8_codepoint_count( $str )
if ( ! function_exists( 'utf8_encode' ) ) :
if ( extension_loaded( 'mbstring' ) ) :
* Converts a string from ISO-8859-1 to UTF-8.
* @deprecated Use {@see \mb_convert_encoding()} instead.
* @param string $iso_8859_1_text Text treated as ISO-8859-1 (latin1) bytes.
* @return string Text converted into a UTF-8.
function utf8_encode( $iso_8859_1_text ): string {
_deprecated_function( __FUNCTION__, '6.9.0', 'mb_convert_encoding' );
return mb_convert_encoding( $iso_8859_1_text, 'UTF-8', 'ISO-8859-1' );
function utf8_encode( $iso_8859_1_text ): string {
_deprecated_function( __FUNCTION__, '6.9.0', 'mb_convert_encoding' );
return _wp_utf8_encode_fallback( $iso_8859_1_text );
if ( ! function_exists( 'utf8_decode' ) ) :
if ( extension_loaded( 'mbstring' ) ) :
* Converts a string from UTF-8 to ISO-8859-1.
* @deprecated Use {@see \mb_convert_encoding()} instead.
* @param string $utf8_text Text treated as UTF-8.
* @return string Text converted into ISO-8859-1.
function utf8_decode( $utf8_text ): string {
_deprecated_function( __FUNCTION__, '6.9.0', 'mb_convert_encoding' );
return mb_convert_encoding( $utf8_text, 'ISO-8859-1', 'UTF-8' );
function utf8_decode( $utf8_text ): string {
_deprecated_function( __FUNCTION__, '6.9.0', 'mb_convert_encoding' );
return _wp_utf8_decode_fallback( $utf8_text );
// 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.
* Performs a case-sensitive check indicating if
* the haystack begins with needle.
* @param string $haystack The string to search in.
* @param string $needle The substring to search for in the `$haystack`.
* @return bool True if `$haystack` starts with `$needle`, otherwise false.
function str_starts_with( $haystack, $needle ) {
return 0 === strpos( $haystack, $needle );
if ( ! function_exists( 'str_ends_with' ) ) {
* Polyfill for `str_ends_with()` function added in PHP 8.0.
* Performs a case-sensitive check indicating if
* the haystack ends with needle.
* @param string $haystack The string to search in.
* @param string $needle The substring to search for in the `$haystack`.
* @return bool True if `$haystack` ends with `$needle`, otherwise false.
function str_ends_with( $haystack, $needle ) {
if ( '' === $haystack ) {
$len = strlen( $needle );
return substr( $haystack, -$len, $len ) === $needle;
if ( ! function_exists( 'array_find' ) ) {
* Polyfill for `array_find()` function added in PHP 8.4.
* Searches an array for the first element that passes a given callback.
* @param array $array The array to search.
* @param callable $callback The callback to run for each element.
* @return mixed|null The first element in the array that passes the `$callback`, otherwise null.
function array_find( array $array, callable $callback ) { // phpcs:ignore Universal.NamingConventions.NoReservedKeywordParameterNames.arrayFound
foreach ( $array as $key => $value ) {
if ( $callback( $value, $key ) ) {
if ( ! function_exists( 'array_find_key' ) ) {
* Polyfill for `array_find_key()` function added in PHP 8.4.
* Searches an array for the first key that passes a given callback.
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
