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function is not described

wp_check_invalid_utf8() WP 2.8.0

Checks for invalid UTF8 in a string.

  • Static. true/false. $is_utf8
  • Static. true/false. $utf8_pcre

No Hooks.

Return

String. The checked text.

Usage

wp_check_invalid_utf8( $string, $strip );
$string(string) (required)
The text which is to be checked.
$strip(true/false)
Whether to attempt to strip out invalid UTF8.
Default: false

Code of wp check invalid utf8: wp-includes/formatting.php WP 5.2.2

<?php
function wp_check_invalid_utf8( $string, $strip = false ) {
	$string = (string) $string;

	if ( 0 === strlen( $string ) ) {
		return '';
	}

	// Store the site charset as a static to avoid multiple calls to get_option()
	static $is_utf8 = null;
	if ( ! isset( $is_utf8 ) ) {
		$is_utf8 = in_array( get_option( 'blog_charset' ), array( 'utf8', 'utf-8', 'UTF8', 'UTF-8' ) );
	}
	if ( ! $is_utf8 ) {
		return $string;
	}

	// Check for support for utf8 in the installed PCRE library once and store the result in a static
	static $utf8_pcre = null;
	if ( ! isset( $utf8_pcre ) ) {
		$utf8_pcre = @preg_match( '/^./u', 'a' );
	}
	// We can't demand utf8 in the PCRE installation, so just return the string in those cases
	if ( ! $utf8_pcre ) {
		return $string;
	}

	// preg_match fails when it encounters invalid UTF8 in $string
	if ( 1 === @preg_match( '/^./us', $string ) ) {
		return $string;
	}

	// Attempt to strip the bad chars if requested (not recommended)
	if ( $strip && function_exists( 'iconv' ) ) {
		return iconv( 'utf-8', 'utf-8', $string );
	}

	return '';
}