_wp_can_use_pcre_u( bool $set = null )

41function _wp_can_use_pcre_u( $set = null ) {42	static $utf8_pcre = null;43 44	if ( isset( $set ) ) {45		_deprecated_argument( __FUNCTION__, '6.9.0' );46	}47 48	if ( isset( $utf8_pcre ) ) {49		return $utf8_pcre;50	}51 52	$utf8_pcre = true;53	set_error_handler(54		function ( $errno, $errstr ) use ( &$utf8_pcre ) {55			if ( str_starts_with( $errstr, 'preg_match():' ) ) {56				$utf8_pcre = false;57				return true;58			}59 60			return false;61		},62		E_WARNING63	);64 65	/*66	 * Attempt to compile a PCRE pattern with the PCRE_UTF8 flag. For67	 * systems lacking Unicode support this will trigger a warning68	 * during compilation, which the error handler will intercept.69	 */70	preg_match( '//u', '' );71	restore_error_handler();72 73	return $utf8_pcre;74}