I use AJAX all the time and never have a problem. All of a sudden every one of my AJAX calls to a variety of server side PHP pages is returning a 200 response and its not recognizing the JSON return. When I visit the PHP page get_message_list.php directly it is perfectly echoing a JSON encoded array as expected {"msg_count":2}, so I know that is correct. If I change the dataType to “text” to test it just outputs the current page HTML. This just started happening and I have no idea what Im doing wrong?!

$.ajax({
    type:'POST',
    url: 'functions/get_message_list.php',
    data:{"test":1},
    contentType: 'application/json;charset=UTF-8',
    dataType   : "json",
    success:function(data){
        
        alert(data.msg_count);
        
    },error: function (request, status, error) {
            alert(request.status);
        }
})

Here is the PHP page code:

session_start();

include_once('../system/db.php');

$my_uid = $_SESSION['user']['user_id'];

$query = "SELECT * FROM msg_connect WHERE from_id = {$my_uid}         
OR to_id = {$my_uid} ";
$result = mysqli_query($connect, $query);
$mail_list_rows = mysqli_num_rows($result);

echo json_encode(array("msg_count"=>$mail_list_rows));
exit();