hi, I am trying to use like in zend

switch($filter2) { case 'name': switch($filter1) { case 'start_with': $search = "\"pd_name like ?\", '$patient_search_name%'"; break;

                                case 'contains':
                                $search = "'pd_name  like ?', '%$patient_search_name%'";
                        break;

                                case 'exact_match': 
                                $search = "'pd_name = ?', $patient_search_name";
                        break;  
                        }
        break;

        case 'phone':
                        switch($filter1)
                        {
                                case 'start_with':
                                $search = "'pd_phone  like ?', '$patient_search_name%'";
                        break;

                                case 'contains': 
                                $search = "'pd_phone  like ?', '%$patient_search_name%'";
                        break;

                                case 'exact_match': 
                                $search = "'pd_phone = ?', $patient_search_name";
                        break;  
                        }
   break;

}
    $select = $this->getDbTable()->select()
                   ->from("patient_data",
                        array('*'))
                       ->where("$search");

but when i see the query log its like

SELECT `patient_data`.* FROM `patient_data` WHERE ("pd_name  like ?", 'bhas%')

where as the ? should have been replaced by the value ....how to solve this??