Drupal Ajax Response caching

ajax_caching.php

/**
 * Implements hook_menu().
 */
function custom_module_menu() {
  $items = array();

  $items['custom-module-ajax'] = array(
    'page callback' => 'custom_module_data_ajax',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}


/**
 * Ajax callback that returns a JSON object.
 */
function custom_module_data_ajax() {
  // Assign the data here. 
  $response = array('a', 'b', 'c');
  $response_json = drupal_json_encode($response);

  // Print the response + the content type header.
  drupal_add_http_header('Content-Type', 'application/json');
  print $response_json;

  // Disable page compression for AJAX requests, because it breaks caching.
  // Browsers don't seem to be able to decompress the return GZIPed json data.
  global $conf;
  $conf['page_compression'] = FALSE;

  // Call this to cache the result of the ajax callback for anonymous users.
  drupal_page_footer();

  // Need to call exit as well, otherwise the html delivery callback will also
  // be executed, and it will try to send headers after the content was sent.
  exit();
}

Check out this one: https://gist.github.com/rogercodina/b1687e078597f60044ff234e84e2f22f