public function isValid(string $string): bool
    {
        if (!isset($string[0])) {
            return true; // Nothing to do.
        }
        return (bool) preg_match('/^./us', $string);
    }
public function isValid(string $string): bool
    {
        if (!isset($string[0])) {
            return true; // Nothing to do.
        }
        return (bool) preg_match('/^./us', $string);
    }
public function isValid ( string $ string ) : bool { if ( ! isset ( $ string [ 0 ] ) ) { return true ; // Nothing to do. } return ( bool ) preg_match ( '/^./us' , $ string ) ; }
Is valid UTF-8?

@since 150424 Enhancing multibyte support.

@param string $string Input string to test.

@return bool True if is valid UTF-8.
Is valid UTF - 8?