Ajax success callback never executed, parsererror

Question

I'm making a simple AJAX call to a server side PHP script but the success callback is never executed. Instead, under the error callback I get the error 'parsererror'. I've searched stackoverflow and have tried everything but nothing works.

If I try to load the URL to the PHP script with relevant fields, in this case http://....../matching.php?cmd=generate&N=2&M=3, I'll get a proper piece of data in JSON format which is returned. For e.g.

{"N":"2","M":"3","E":[[1,1,39],[0,3,100],[2,1,50]]}

AJAX CALL

$('form').on('submit', function(event) {
        event.preventDefault();
        $.ajax({
            url: 'matching.php',
            dataType: 'json',
            contentType: 'json',
            type: 'GET',
            data: {
                cmd: "generate",
                N: $('#n1').val(),
                M: $('#n2').val()
            },
            success: function(data) {
                alert(data);
                leftCount = data.N;
                rightCount = data.M;
                returnedArray = data.E;
                generateFirstPage();
            },
            error: function(request,error) { 
                alert(request.responseText);
                alert(error);
            }
        });

    })

PHP

<?php

if (isset($_GET['cmd'])) {
    $n = $_GET["N"];
    $m = $_GET["M"];
    echo json_encode(generateEdges($n, $m));
    exit;
}

function generateEdges($n, $m) {
    $edgeNumber = rand($n,$n*2);
    $e = array();
    for($i=0; $i<$edgeNumber; $i++) {
        array_push($e, array(rand(0,$n), rand(0,$m), rand(1,100)));
    }
    return $finalArray = array('N' => $n, 'M' => $m, 'E' => $e);
}

?>

Doing a console.log(request.reponseText) will give

{"N":"2","M":"3","E":[[1,0,42],[1,3,48],[0,3,44],[0,0,8]]}

Take out everything in your php file that's not inside the php tag. — jessica, Feb 29 '16 at 17:48
The script src should be inside the first file, not the second. — jessica, Feb 29 '16 at 17:49
@jessica the first file is a .js file. why would i put the script src in there? also i've taken out everything that isn't in the php tag. I still get parsererror — CHEWWWWWWWWWW, Feb 29 '16 at 17:53
All JavaScript codes should be in the file where you make the Ajax call, or they won't be executed. Are you getting the parse error when you first load the page, or when you first execute the ajax call? — jessica, Feb 29 '16 at 17:56
@jessica as mentioned above. the error callback is executed which gives the parsererror — CHEWWWWWWWWWW, Feb 29 '16 at 17:57
@jessica you can explain what regular ajax is as oppose to json. there are no errors in the console. the error has something to do with the data which is being returned. if someone can outrightly tell me that the data being passed back is NOT json when i specified my dataType as json then we all know where the error is. but at this point. it looks like that isn't the case — CHEWWWWWWWWWW, Feb 29 '16 at 18:02
`{"N":"2","M":"3","E":[[1,0,42],[1,3,48],[0,3,44],[0,0,8]]}` this is valid json @NabinKunwar — santosh, Feb 29 '16 at 18:32
another option could be to remove `contentType` and `dataType` and let the ajax call detect it automatically, http://stackoverflow.com/a/16013156/2337692. — jnersn, Feb 29 '16 at 18:42

score 0 · Answer 1 · answered Feb 29 '16 at 19:40

I believe the error is that your AJAX call isn't actually hitting your matching.php file. I copied your code into 2 files of my own, 1 with the HTML and the javascript included (though I did wrap the javascript with a $(document).ready(function() { ... }), but that doesn't seem to be your problem).

When I hit submit, calling my own "matching.php" but leaving that file empty, I get the same parsererror you mention. If I then have matching.php execute the code you provided, it hits the success condition and everything is fine. I don't think the issue is the PHP or even your javascript, necessarily, just where it's looking for matching.php.

Use Firebug or Chrome's developer javascript console to view the ajax network call to see if it actually hits it. This may just be a symptom of a different problem, but it's worth double checking, imo.

Ajax success callback never executed, parsererror

1 Answers1