geting error while distributing team member

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PHP

dear all user i m getting error while distributing team member from data base

if(isset($_POST['searchuser']))
{
     $depart=$_POST['searchdepart'];
     $desig=$_POST['searchdesig'];
    $select=mysql_query("SELECT * FROM admin_login WHERE depart='$depart' and designation='$desig' ");
     $numb=mysql_num_rows($select);
        while($row=mysql_fetch_array($select))
                {

$id=$row['UId'];
$data=$row['loginid'];
$email=$row['email'];
$depart=$row['depart'];
$designation=$row['designation'];


?>

this is ajax code which im using

<script>
function showDesig(str) {
    if (str.length == 0) {
        document.getElementById("txtHint").innerHTML = "";
        return;
    } else {
        var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                document.getElementById("txtHint").innerHTML = xmlhttp.responseText;
            }
        }
        xmlhttp.open("GET", "../assign_team.php?asgwrk=" + str, true);
        xmlhttp.send();
    }
}

function isNumber(evt) {
    evt = (evt) ? evt : window.event;
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        return false;
    }
    return true;
}
</script>

assignteam.php

<?php
include("includes/connection.php");
$id=$_GET['asgwrk'];
if($id=='TechSales')
{?>
  <select name="searchdesig" id="searchdesig" style="height:19px;float:left;width:40%;height:25px;margin-left:10px;">
                        <option value="0">Choose Designation</option>
                      <option value="supervisor">supervisor</option>
                        <option value="agent">agent</option>

                    </select>
<?php  }

else if($id=='customer_service')
{
?>
 <select name="searchdesig" id="searchdesig" style="height:19px;float:left;width:40%;height:25px;margin-left:10px;">
                        <option value="0">Choose Designation</option>
                        <option value="supervisor">supervisor</option>
                        <option value="agent">agent</option>

                    </select>
<?php
}
else if($id=='TechSupport')
{
?>

<select name="searchdesig" id="searchdesig" style="height:19px;float:left;width:40%;height:25px;margin-left:10px;">
                        <option value="0">Choose Designation</option>
                       <option value="supervisor">supervisor</option>
                        <option value="agent">agent</option>
                    </select>

<?php
}
?>

getting error :

Notice: Undefined index: searchdesig in C:\xampp\htdocs\admin_panel\Admin\teamdistribution.php on line 42