seems_utf8( string $str ): bool

883function seems_utf8( $str ) {884	mbstring_binary_safe_encoding();885	$length = strlen( $str );886	reset_mbstring_encoding();887 888	for ( $i = 0; $i < $length; $i++ ) {889		$c = ord( $str[ $i ] );890 891		if ( $c < 0x80 ) {892			$n = 0; // 0bbbbbbb893		} elseif ( ( $c & 0xE0 ) === 0xC0 ) {894			$n = 1; // 110bbbbb895		} elseif ( ( $c & 0xF0 ) === 0xE0 ) {896			$n = 2; // 1110bbbb897		} elseif ( ( $c & 0xF8 ) === 0xF0 ) {898			$n = 3; // 11110bbb899		} elseif ( ( $c & 0xFC ) === 0xF8 ) {900			$n = 4; // 111110bb901		} elseif ( ( $c & 0xFE ) === 0xFC ) {902			$n = 5; // 1111110b903		} else {904			return false; // Does not match any model.905		}906 907		for ( $j = 0; $j < $n; $j++ ) { // n bytes matching 10bbbbbb follow?908			if ( ( ++$i === $length ) || ( ( ord( $str[ $i ] ) & 0xC0 ) !== 0x80 ) ) {909				return false;910			}911		}912	}913 914	return true;915}