code: function getIdentifiers($as_string = true) {
  		$ident = array_keys($this->identifiers);
  		return (($as_string) ? implode('', $ident) : $ident);
  	}
docs: Returns identifier characters as string/array
  @param bool $as_string Should the result be a string or an array?
  @return string|array
  @see setIdentifiers()