select option selection in php - php

Question

I have a form for input order, there are 2 fields, branch and customer model. Before we click button "search", we must select branch and customer fields. After I filled the field, then click button search, the data appears. The problem is, after the data appears, where the condition branch and customer models are filled, I want to create another search, then I changed branch field only (customer model field was same with the previous search), change branch field from 'A' to 'B' and click button search, the data not appears / empty (whereas the data exists in database). Branch field,the field when I changed into B, after I click button search, the branch filled changed into
'SELECT' (branch option are SELECT -> A , B).
I'm confused with this problem.. here is the 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 = $db->GetAll("select cab_id, cabang_name from company_profile where cab_id in(".$branch.")");
?>
<td>Branch :</td>
<td>
<select id="branch" name="branch">
<option value="0">Select</option>
<?php foreach($check_data as $row): ?>
<option <?php echo ($_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);
}