Display Table based on dropdownlist selection in PHP - php

Question

My table is not displayed when i select any project name. I guess the onchange function is not working properly but i couldn't figure out the problem.
Code is as follows:
<div class="span6">
<?php $sql = "SELECT * from login_projects WHERE login_id='".$record['login_id']."'";
$res_sql = mysql_query($sql); ?>
<label>Project Name <span class="f_req">*</span></label>
<!--<input type="text" name="city" class="span8" />-->
<select name="project_name" onchange="get_list_onnet()" id="project_name" class="span8">
<option value="">--</option>
<?php while($rec_sql = mysql_fetch_array($res_sql)){ ?>
<option value="<?php echo $rec_sql['project_id']; ?>">
<?php echo $rec_sql['project_name']; ?></option>
<?php } ?>
</select>
</div>
Function:
<script>
function get_list_onnet(){
var project_name=$("#project_name").val();
$.ajax
({
type: "POST",
url: "ajax.php",
data: {action: 'get_list_onnet',list_onnet:project_name},
success: function()
{
document.getElementById("dt_a").style="block";
$("#dt_a").html(html);
}
});
};
</script>
<script>
$(document).ready(function() {
//* show all elements & remove preloader
setTimeout('$("html").removeClass("js")',1000);
});
</script>
Ajax.Php Page:
function get_list_onnet(){
$list_onnet=$_POST['list_onnet'];
$sql_list_onnet=mysql_query("SELECT * from projects,project_wise_on_net_codes
where projects.project_id = project_wise_on_net_codes.project_id AND
project_wise_on_net_codes.project_id='$list_onnet'");
$row1 = mysql_num_rows($sql_list_onnet);
if($row1>0)
{
echo "<tr><th>id</th><th>Project Name</th><th>Country Code</th><th>On-net prefix</th>
<th>Action</th></tr>";
$k = 1; while($row_list_onnet=mysql_fetch_array($sql_list_onnet))
{
$project3 = $row_list_onnet['project_name'];
$countrycode1 = $row_list_onnet['country_code'];
$prefix1 = $row_list_onnet['on_net_prefix'];
$id_proj = $row_list_onnet['project_id'];
$on_prefix = $row_list_onnet['on_net_prefix'];
echo "<tr><td>".$k."</td><td>".$project3."</td><td>".$countrycode1."</td>
<td>".$prefix1."</td><td><a href='process/update_process_onnet.php?ID=".$id_proj."&Onnet=".$on_prefix."'>Delete</a></td>
</tr>";
$k++;
}
}
else
{
echo "<script>alert('No Record Found')</script>";
}
}
The problem is that it is always going in the else condition and nothing is displayed in the table.