Why does jquery ajax callback function not work?

Question

I am having a problem with a simple callback function in jQuery ajax. Google won't help and stack overflow wouldn't either, so I guess this might not be something specific but rather something I am too ignorant to see. To me the code looks exactly like it should.

So, here's the code:

function sendMessage(message)
{
//Establish connection to php script
$.ajax({
    type: 'POST',
    url: 'action/chat/test.php',
    success: function(feedback){

        alert(feedback);

    }
}).error(function(){
    //Do some error handling here
});
}

In test.php it simply says

<?php
    echo "called";
?>

As far as I am concerned "called" should be alerted - but it isn't. I have checked already that the function sendMessage() is called (and the parameter message doesn't matter for now).

Does anyone have any idea?

If you put an alert at the beginning of sendMessage(), does it show? — jfriend00
– jfriend00, Commented May 2, 2012 at 21:55
The two likeliest options: Javascript errors causing the AJAX request not to be sent, or a problem with the AJAX request that means the error, rather than success, callback function is executed. Using your browsers debugger would be a good first step. — Anthony Grist
– Anthony Grist, Commented May 2, 2012 at 21:55
Does it work if you visit action/chat/test.php in your browser? Do you server logs show that file being hit when you run the AJAX? — jimw
– jimw, Commented May 2, 2012 at 21:56

Fostah · Accepted Answer · 2012-05-03 22:39:18Z

13

Update: One thing to note also, make sure you use some kind of debugger like firebug. Then you can go to the network tab and look at the request url and response manually to see if its getting a 200 response or internal server error, etc.

Try adding a console.log(data); in your success function to see if anything is being returned.

You could also use .always(data):

function sendMessage(message)
{
  //Establish connection to php script
  $.ajax({
      type: 'POST',
      url: 'action/chat/test.php'   
  }).done(function(data) { console.log(data); })
    .fail(function() { alert("error"); })
    .always(function() { alert("complete"); });
}

From the docs:

Deprecation Notice: The jqXHR.success(), jqXHR.error(), and jqXHR.complete() callbacks will be deprecated in jQuery 1.8. To prepare your code for their eventual removal, use jqXHR.done(), jqXHR.fail(), and jqXHR.always() instead.

edited May 3, 2012 at 22:39

answered May 2, 2012 at 22:01

Fostah

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2 Comments

Dennis Hackethal Over a year ago

I have found the problem! There was some issue with file access from my apache. Apache was not allowed to read the file - although I just created it with Coda as I usually do. Now the callback works. I just joined stack overflow and have to say that I am overwhelmed with all the quick answers! Thank you!

Fostah Over a year ago

One thing to note also, make sure you use some kind of debugger like firebug. Then you can go to the network tab and look at the request url and response manually to see if its getting a 200 response or internal server error, etc.

Nadir · Accepted Answer · 2014-07-29 09:50:10Z

4

Just for the reference, there is a behavior that may end up like this (ie done() not called).

Here it is:

Suppose you expect a JSON object (you asked for it with the "Accept" mime type).
Suppose the Json string is not valid.

In this case done() is never called, but always() will be. And in always() you will get the "badly" formatted answer as pure text.

answered Jul 29, 2014 at 9:50

Nadir

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Comments

DanRedux · Accepted Answer · 2012-05-02 21:55:51Z

1

It's probably the error handling. If you want to handle errors, there's another attribute you can give the object you pass in to ajax, it's "error", and also "timeout" for handling page timeouts. Look up the $.ajax function and you'll find these attributes.

answered May 2, 2012 at 21:55

DanRedux

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2 Comments

Dennis Hackethal Over a year ago

When I tried to use the error handling before with an alert, it didn't alert anything. Now it does. There seems to be something wrong with the php file, although the path is correct.

Dennis Hackethal Over a year ago

I have found the problem! There was some issue with file access from my apache. Apache was not allowed to read the file - although I just created it with Coda as I usually do. Now the callback works. I just joined stack overflow and have to say that I am overwhelmed with all the quick answers! Thank you!

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