Php Codeigniter Order By Field function

	/**
	 * Order By Field
	 *
	 * Order By Field allows you to specify the order
	 * of an MySQL result - useful if you want to
	 * order by a where_in() query.
	 *
	 * @param string $row
	 * @param  array/string $values
	 * @return object
	 */
	function order_by_field($row, $values) {
		/* Clean the row */
		$row = $this->_protect_identifiers($row);
	 
		/* Clean and implode the values */
		if(is_array($values)) {
		   foreach($values as $key => $value) {
			   $values[$key] = $this->escape($value);
		   }
		   $values = implode(',', $values);
		} else {
		   $values = $this->escape($value);
		}
	 
		/* Build the query */
		$query = "FIELD({$row}, {$values})";
	 
		$this->ar_orderby[] = $query;
		return $this;
	}