How can I check if a request is an AJAX request?

Question

I am looking for a Drupal way of detecting AJAX request. I need to check this inside hook_form_alter() when embedding views with AJAX support.

How can I understand a request is an AJAX request?

Answer 1

For Drupal 7 there's nothing special in the API, just use plain PHP:

if (!empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
  // AJAX request
}

For Drupal 8, the Symfony request object has a helper method:

// Example for brevity only, inject the request_stack service and call 
// getCurrentRequest() on it to get the request object if possible.
$request = \Drupal::request();
$is_ajax = $request->isXmlHttpRequest();

Answer 2

You may consider using 'current_path()` and verify the path contains ajax in it.

$current_path = current_path();
if (strpos($current_path, 'ajax') !== FALSE) {
  // This is an AJAX request.
}

Answer 3

AJAX request in scope of working with forms in Drupal would mean that form must be rebuild. To detect that form must be rebuild one should check for:

$form_state['rebuild'] == TRUE;

Answer 4

Since there is no bullet-proof method of checking AJAX request (as HTTP_X_REQUESTED_WITH can be spoofed), here is another alternative based on the URL:

if (end((arg())) == 'ajax') {
  // AJAX request
}

Works for views (in case when last URI item contains 'ajax' word).

See also: How to check if the request is an AJAX request with PHP?

Answer 5

How I did it was using:

$request = $_SERVER['REQUEST_URI']

There I detected the ?_wrapper_format=drupal_ajax