select option selection in php -

i have form input order, there 2 fields, branch , customer model. before click button "search", must select branch , customer fields. after filled field, click button search, data appears. problem is, after data appears, condition branch , customer models filled, want create search, changed branch field (customer model field same previous search), change branch field 'a' 'b' , click button search, data not appears / empty (whereas data exists in database). branch field,the field when changed b, after click button search, branch filled changed

'select' (branch option select -> , b).

i'm confused problem.. here code :

<?php    if ($_post)    {       $_session['data_id'] = $_post['data_id'];       $_session['branch'] = $_post['branch'];       $_session['customer_model'] = $_post['customer_model'];     }  ?>  <form id="search" class="formular" method="post" action="search_data.php" style="z-index:1;">    <table width="100%">      <tr>        <td>data id :</td>          <td><input type="text" name="data_id" value="<?php echo $_session['data_id'];?>"></td>      </tr>      <tr>         <?php             $branch = "'".str_replace(",", "','", $_session['moi_status_userbranch'])."'";             $check_data = $db->getall("select cab_id, cabang_name company_profile cab_id in(".$branch.")");         ?>         <td>branch :</td>         <td>             <select id="branch" name="branch">                     <option value="0">select</option>                 <?php foreach($check_data $row): ?>                     <option <?php echo ($_session['branch'] == $row['cab_id']) ? "selected" : ""; ?> value="<?php echo $row['cab_id']; ?>"><?php echo $row['cabang_name']; ?></option>                 <?php endforeach; ?>             </select>         </td>       </tr>       <tr>         <td width="110">customer model</td>         <td>             <select id="customer_model" name="customer_model" class="readonly validate[required]">                 <option <?php echo ($_session['customer_model'] == '0') ? "selected" : ""; ?> value="0">pilih</option>                 <option <?php echo ($_session['customer_model'] == 'i') ? "selected" : ""; ?> value="i">personal</option>                 <option <?php echo ($_session['customer_model'] == 'c') ? "selected" : ""; ?> value="c">corporate</option>             </select>         </td>     </tr> </table> <input type="submit" id="btnsubmits" name="btnsubmit" class="button" value="search" /> <a onclick="mypopup();" style="text-decoration:underline; cursor:pointer; font-weight:bolder">add new</a> </form> <script> function mypopup()    {       <?php unset($_session['regional_saved']); ?>       mywindow = window.open("choose_custtype.php" ,"item","width=700px,height=350px,resizable=1,scrollbars=1,top=150,left=200");       mywindow.moveto(200, 200);    }