Zend_Db_Table_Abstract::_where PHP Method

    protected function _where(Zend_Db_Table_Select $select, $where)
    {
        $where = (array) $where;
        foreach ($where as $key => $val) {
            // is $key an int?
            if (is_int($key)) {
                // $val is the full condition
                $select->where($val);
            } else {
                // $key is the condition with placeholder,
                // and $val is quoted into the condition
                $select->where($key, $val);
            }
        }
        return $select;
    }