public static function validateString($data, callable $filter=null) {
        if ( is_string($data) === false ) return false;
        return self::applyFilter($data, $filter);
    }
public static function validateString($data, callable $filter=null) {
        if ( is_string($data) === false ) return false;
        return self::applyFilter($data, $filter);
    }
public static function validateString ( $ data , callable $ filter = null ) { if ( is_string ( $ data ) === false ) return false ; return self :: applyFilter ( $ data , $ filter ) ; }
String validator.

@param mixed $data Data to validate
@param callable $filter Custom filter
@return bool
String validator .