No data returning from ajax $.post()

I am having trouble getting any response text from my jQuery AJAX post:

$('document').ready(function()
{

    $('#saveRouteTrace').click(function(){

        // Build latStr and lonStr
        if(saveCha开发者_StackOverflownges()) {
            $.post('changeRouteTrace.php', {    
                    id: traceRouteId 
                   },
            function(data) {
                if(data.success) {
                    alert(data.reason);
                }
                else {
                    alert("Error: " + data.reason); 
                }                   
            }, 'json');
        }
    });
});

I am returning a response like:

{ "success": true, "reason": "because it worked" }

from the server, but the function(data) code never executes. What am I doing wrong?

You can check using FireBug if the request is sent and if the response looks ok. If the request is sent, but you don't get a proper response, it may be easier to create a test form in HTML and post the data using that form. Debugging that is easier than using the javascript response, because you can just keep refreshing after a change and check the response in the browser.

Assuming your savechanges() function returns a value, this code snapshot works fine in my system.

$(document).ready(function(){

    $('#saveRouteTrace').click(function(){

        // Build latStr and lonStr
        if(saveChanges()) {
            $.post('stackoverflowajax.php', {    
                    id: 9,
                    name:'Tsegay' 
                   },
            function(data) {
                    alert(data);
                if(data.success) {
                    alert(data.reason);
                }
                else {
                    alert("Error: " + data.reason); 
                }                  
            }, 'json');
        }
    });
        function saveChanges(){
            //This is a debuging code ... Make sure it return a value
                return true;
            }
    });

This is the file on the server side. I am echoing the json file.

if(isset($_POST['id'])){
            //This do not work
            return '{ "success": true, "reason": "because it worked" }';
        //this works fine
        echo '{ "success": true, "reason": "because it worked" }';
    }