ajax catch correct error code

i have this little code to post to my server

    $.ajax({
      type: 'POST',
      url: 'post.php',
      data: { token: '123456', title: 'some title', url: 'http://somedomain.com', data: '' },
      success: function(data){
        alert (data)
      }
    });        

Wondering how i can "catch" the different errors for ajax request: f开发者_如何学Goor eg, post.php return 'token error' when invalid token has been posted, or 'invalid title' for missing title.

Thanks in advance

If the server sends something else than 200 status code you could use the error handler:

$.ajax({
    type: 'POST',
    url: 'post.php',
    data: { 
        token: '123456', 
        title: 'some title', 
        url: 'http://somedomain.com', 
        data: '' 
    },
    success: function(data){
        alert(data);
    },
    error: function() {
        alert('some error occurred');
    }
}); 

If your server performs some validation on the request arguments maybe it could return a JSON object containing the error information (and set the proper Content-Type: application/json):

{ error: 'some error message' }

In this case you could handle this in the success callback:

success: function(data) {
    if (data.error != null && data.error != '') {
        // TODO: the server returned an error message
        alert(data.error);
    } else {
        // TODO: handle the success case as normally
    }
}

// build the initial response object with no error specified
$response = array(
  'error' => null
);

// the data checks went fine, process as normal
if (data is ok) {
  $response['some_object'] = value;

// something is bad with the token
} else if (bad token) {
  $response['error'] = 'token error';

// something is bad with the title
} else if (bad title) {
  $response['error'] = 'bad title';

// some other error occured
} else {
  $response['error'] = 'unspecified error';
}

// output, specifying that it's JSON data being returned
header('Content-Type: application/json');
echo json_encode($response);

and....

// $.ajax({ ...
success: function(data){
  if (!data.error){
    alert('OK!');
  }else{
    alert('Error: '+data.error);
  }
}
// });

Something like that perhaps? (Unless you're talking legitimate AJAX errors, in which case supply the error: function(x,t,e){} ajax option or use .ajaxError)

What I like to do is set the dataType for the $.ajax() to 'json' and then in the PHP page you can just echo a json_encode()ed associative array. This will let you reference the values via your function parameter data (i.e. data.success, data.message). Let me know if you need some examples.

You probably want to set the 'error' handler function, which would treat the error you received.

Take a look at http://api.jquery.com/jQuery.ajax/ in the error setting.