system/classes/Db_MySQL.php
public static function parseArray($param, $values)
    {
        $str = "";
        foreach($values as $index => $value){
          $str .= $param.$index.",";
        }
        return rtrim($str,",");     
    }
public static function parseArray($param, $values)
    {
        $str = "";
        foreach($values as $index => $value){
          $str .= $param.$index.",";
        }
        return rtrim($str,",");     
    }
Returns a string representing an array where each element is bound.
Giving it ":id" for the param would result in:
":id1,:id2,:id3", etc