AJAX Form Submission Not Querying PHP - php

Question

Trying to use AJAX to submit form data to a PHP file. Everything in the code seems to work except for a call to the PHP file.
I setup a Java Alert() on the PHP file and it never alerts.
I am sure it is an issue with the AJAX code but I don't know it well enough to figure out what is going wrong.
The AJAX Call:
$(document).on('click','.addItem',function(){
// Add Item To Merchant
var el = this;
var id = this.id;
var splitid = id.split("_");
// Add id's
var addid = splitid[1]; // Merchant ID
var additem = splitid[2]; // Item ID
// AJAX Request
$.ajax({
url: "jquery/addItem.php",
type: "POST",
data: { mid : addid , iit : additem },
success: function(response){
// Removing row from HTML Table
$(el).closest('tr').css('background','tomato');
$(el).closest('tr').fadeOut(300, function(){
$(this).remove();
});
}
});
});
The HTML Form Call Within a Table:
<span class='addItem' id='addItem_<?php echo $m; ?>_<?php echo $list['id']; ?>' >Add Item</span>
Ok Simple PHP code that it calls to with some alerts for testing:
<?php
require_once("../includes/constants.php");
require_once("../includes/functions.php");
$iid = filter_input(INPUT_POST, 'iit', FILTER_SANITIZE_STRING); // Item ID
$mid = filter_input(INPUT_POST, 'mid', FILTER_SANITIZE_STRING); // Merchant ID
$slot = 0;
$slot = getMerchSlot($mid);
?>
<script>
alert ("Slot Value: <?php echo $slot; ?>");
</script>
<?php
$result = $pdoConn->query("INSERT INTO merchantlist (merchantid, item, slot)
VALUES
('$mid', '$iid', '$slot') ");
if ($result) {
?>
<script>
alert("Looks like it worked");
</script>
<?php
}
echo 1;
?>