Commerce Hook Function To Checkout Button

Question

I am a Drupal Commerce novice. I have a basic cart system working fine, but I now need to get into some custom code. I don't think I can use Rules because the code is a bit too complicated.

I have a Shopping Cart page with a Checkout button. I want to hook into that Checkout button.

I need to add a php function (which I already have) which will execute when that button is clicked but -before- the checkout page is rendered.

And I need this to do so without disabling the default actions that the Checkout button performs.

SO: How do I hook into this button without disabling the default behaviour?

Due to my noobness--I'd appreciate as complete an example as possible. I'm not lazy, just can't take for granted that I'll catch everything I need to if the answer is 'shorthand'.

TIA,

---JC

Answer 1

The checkout form is a form like any other, so you can just alter it (using hook_form_alter()) and add a submit handler:

function MYMODULE_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'views_form_commerce_cart_form_default') {
    $form['#submit'][] = 'MYMODULE_some_function';
  }
}

function MYMODULE_some_function($form, &$form_state) {
  drupal_set_message('This was run after the cart form was submitted, before the checkout page was rendered.');
}

Addressing the comments...

As you have a custom shopping cart form, with a link instead of submit button, no extra processing will be done so you can just hook into the page build of the linked page (/checkout/%) and perform your operation there; it will have the same effect.

There are a couple of places you could do this (neither really 'better' than the other), hook_page_alter() and hook_init(). There are other places too (theme preprocess functions) but for processing logic something a bit earlier is probably more appropriate. Basic example (will probably need tweaking for your needs):

function MYMODULE_init() {
  if (arg(0) == 'checkout' && $some_other_pertinent_condition) {
    // Do some processing.
  }
}

As for learning Commerce - that's a tricky one. Commerce is heavily integrated with Drupal and uses a lot of its functions/hooks/integrations just like any other module would. So really you need to know Drupal's workflow, and then overlay Commerce's workflow on top of that. The best advise I can give is to grab a Drupal book (Pro Drupal Development is excellent), and after you're happy with the workflow there, hit the Drupal Commerce support pages and read, read, read.

Drupal has a notoriously steep learning curve, and there isn't really a shortcut to understanding how it works as a whole. You just have to get stuck in. But it's well worth it, Drupal's awesome.

Answer 2

Yikes. As far as I can tell, there isn't a direct hook for clicking the checkout button. The provided hooks for the Drupal Commerce checkout module are over here, there's a general hooks list here, and the actual checkout form output is generated here which can be overridden.

This is a tricky request, and I'm at a loss. The test site I set up doesn't even show the checkout button in a form, it's just a link - so I guess you can't use hook_form_alter() on it.

My thoughts for chasing this down are:

• Add some custom JS and make an ajax call on button click that initiates a condition for the next page
• Start logging the previous page in a session variable and do a comparison when you land on the checkout page - if you came from a page that has a checkout button, execute action. (Might be able to adapt Previous Pages for use)
• Use Rules to trigger on a "Product is viewed" action with a path condition of the checkout page
• Hook into the checkout_page_info_alter function to determine whether you're on the correct page
• Redirect users to a staging page of sorts before they hit the actual checkout page - change the cart page to something of your own choosing, collect some data, append a ?destination parameter to the URL and roll through with your new info

I'm at a loss. Since this isn't really an answer, I can't give a great example of how to do any of this without great detail. I did figure out the Commerce hooks for you though:

hook_commerce_cart_order_is_cart_alter becomes YOURTHEME_commerce_cart_order_is_cart_alter

Lol. Sorry for not being more useful... good luck.