code: protected static function unescapeString($matches) {
  		static $map = ['n' => "\n", 'r' => "\r", 't' => "\t", 'v' => "\v", 'f' => "\f"];
  		
  		if (!empty($matches[2]))
  			return chr(octdec($matches[2]));
  		elseif (!empty($matches[3]))
  			return chr(hexdec($matches[3]));
  		elseif (isset($map[$matches[1]]))
  			return $map[$matches[1]];
  		
  		return $matches[1];
  	}
docs: Replaces special characters in a string
  @param array $matches
  @return string