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<?php

/**
 * Implements hook_form_FORM_ID_alter(): views_form_commerce_cart_form_default.
 */
function MODULENAME_form_views_form_commerce_cart_form_default_alter(&$form, &$form_state) {
  $form['#action'] = url('cart');
 
  // AJAX button "Update cart"
  $form['actions']['submit']['#name'] = 'update-cart';
  $form['actions']['submit']['#ajax'] = array(
    'callback' => 'MODULENAME_cart_form_ajax_update',
  );
 
  // AJAX quantity inputs
  foreach (element_children($form['edit_quantity']) as $key) {
    $form['edit_quantity'][$key]['#ajax'] = array(
      'callback' => '',
      'event' => 'keyup',
      'progress' => 'none',
      'trigger_as' => array(
        'name' => 'update-cart',
      )
    );
  }
}
 
/**
 * AJAX update cart.
 */
function MODULENAME_cart_form_ajax_update($form, &$form_state) {
  drupal_get_messages();
  $_POST = array();
  $order_id = commerce_cart_order_id($GLOBALS['user']->uid);
  $cart = commerce_embed_view('commerce_cart_form', 'default', array($order_id));
  return array(
    '#type' => 'ajax',
    '#commands' => array(
      ajax_command_replace('.view-commerce-cart-form', $cart),
    ),
  );
}