Help with hook_form_alter So I've got a custom module that builds a page (/simple-ajax-form) and has a form on it with the ID "payment_form" and other fields with IDs like "number_1". My module name is "Drupalup Simple Custom Form" for reference. 

The problem I can't figure out (as I'm new to hook_form_alter) is that on the form ID instead of it being "payment_form" the ID gets rendered as "payment-form" and then on the input fields instead of it being "number_1" the ID get rendered as "edit-number-1".

What code do I need to make the form render as "payment_form" and inputs without "edit" and to also have underscores? And where does this code go - in my custom module?
Figured it out - put it the ID request in to an array: 

$form['#attributes'] = array('id' =&gt; array('payment_form'));

Instead of 

public function getFormId() { return 'payment_form'; }