_mb_substr()
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.
Internal function — this function is designed to be used by the kernel itself. It is not recommended to use this function in your code.
No Hooks.
Return
String
. Extracted substring.
Usage
_mb_substr( $str, $start, $length, $encoding );
- $str(string) (required)
- The string to extract the substring from.
- $start(int) (required)
- Position to being extraction from in $str.
- $length(int|null)
- Maximum number of characters to extract from $str.
Default: null - $encoding(string|null)
- Character encoding to use.
Default: null
Changelog
Since 3.2.0 | Introduced. |
_mb_substr() mb substr code WP 6.5.2
function _mb_substr( $str, $start, $length = null, $encoding = null ) { if ( null === $str ) { return ''; } 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 ( ! in_array( $encoding, array( 'utf8', 'utf-8', 'UTF8', 'UTF-8' ), true ) ) { 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 ); } $regex = '/( [\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} )/x'; // Start with 1 element instead of 0 since the first thing we do is pop. $chars = array( '' ); do { // We had some string left over from the last round, but we counted it in that last round. array_pop( $chars ); /* * 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 ) ); }