Dynamic drowndown using Ajax and PHP is showing blank - php

Question

Below is my AJAX script used for dynamic multiselect.
The issue is it give blank option in my second drop down.
Can anyone plz help me to debug.
Also it worked in test when deployed to live its not functioning.
Any help will really help
<script>
function getmodels1(val) {
alert(val.value);
$.ajax({
type: "POST",
url: "get_models.php",
data:'compid='+val,
success: function(data){
$("#cname").html(data);
}
});
}
function selectCountry(val) {
$("#search-box").val(val);
$("#suggesstion-box").hide();
}
</script>
Below is my form
<div class="form-group">
<label class="col-sm-2 control-label">Car Company</label>
<div class="col-sm-10">
<select onChange="getmodels1(this.value);" name="ccompany" id="ccompany" class="form-control" >
<option value="">Select</option>
<?php $query =mysqli_query($con,"SELECT * FROM tblcompany");
while($row=mysqli_fetch_array($query))
{ ?>
<option value="<?php echo $row['compid'];?>"><?php echo $row['CompanyName'];?></option>
<?php
}
?>
</select> </div>
</div>
<div class="form-group">
<label class="col-sm-2 control-label">Car Name</label>
<div class="col-sm-10">
<select name="cname" id="cname" class="form-control">
<option value="">Select</option>
</select>
</div>
</div>
Below is my getmdels PHP
<?php
include('includes/dbconnection.php');
if(!empty($_POST["compid"]))
{
$query =mysqli_query($con,"SELECT * FROM tblmodels WHERE compid = '" . $_POST["compid"] . "'");
?>
<option value="">Select Models</option>
<?php
while($row=mysqli_fetch_array($query))
{
echo 'Success'
?>
<option value="<?php echo $row["id"];?>"> <?php echo $row["models"];?></option>
<?php
}
}
?>

Answer 1

#Nischal
In get_models.php You are just looping the option inside while.
Instead of the line <option value="<?php echo $row["id"];?>"> <?php echo $row["models"];?></option> add echo statement echo '<option value="'.$row["id"].'">'.$row["models"].'</option>';
Don't forget to remove echo 'Success' message there.

Answer 2

I think the problem lies in the getmodel.php file
mysqli_query($con,"SELECT * FROM tblmodels WHERE compid = '" . $_POST["compid"] . "'");
Instead of using '.' please use the PHP string interpolation so it will be easy for you to concatenate the string with PHP variables.
Try this,
`mysql_query($con, "SELECT * FROM tblmodels WHERE compid = '{$_POST["compid"]}'");`
And you are also displaying success which might cause a problem.