public function field($fieldnames) {

		$fieldnames = func_get_args();

		foreach($fieldnames as $fieldname) {

			if(false === is_string($fieldname)) {
				return trigger_error(sprintf('All fieldnames used in "%s"() must be of the type string, "%s" given', __METHOD__, gettype($fieldname)), E_USER_ERROR);
			}
		}

		$this -> setFieldnames($fieldnames);

		return $this;
	}