How to use form validation in Drupal 7 - forms

Question

I am trying to edit the checkout form in Drupal Commerce, to require a user to enter their email address twice. When they submit their form, Drupal should check to see if the emails match, and call form_set_error() if they don't. For now, I am just trying to attach a custom validation function to the form, which I can't get to work. (My module is called checkout_confirm_email. This module is only for our own use, so I didn't put much effort into the name).
function checkout_confirm_email_form_alter(&$form, &$form_state, $form_id) {
if($form_id == 'commerce_checkout_form_checkout') {
$form['#validate'][] = 'checkout_confirm_email_form_validate';
dprint_r($form['#validate']);
dsm("I printed");
}
}
function checkout_confirm_email_form_validate($form, &$form_state) {
dsm("Never prints...");
}
The dprint_r statment outputs Array ([0] => checkout_confirm_email_form_validate). So the function is part of the form array, but the dsm statement in the validation function never prints.
I've actually been stuck for a while. I've looked up examples, and I can't see what I'm doing wrong. Anyone?

Answer 1

You need to attach the #validate property to the form submit button like this:
$form['submit']['#validate'][] = 'checkout_confirm_email_form_validate'
And it'll work then it's not necessary that my example is identical match to your form tree you should search for the submit button array and apply this example to it

Answer 2

Instead of form_set_error() I would use form_error($form, t('Error message.'));
function checkout_confirm_email_form_alter(&$form, &$form_state, $form_id) {
if($form_id == 'commerce_checkout_form_checkout') {
$form['#validate'][] = 'checkout_confirm_email_form_validate';
dpm($form['#validate']);
dsm("I printed");
}
}
function checkout_confirm_email_form_validate(&$form, &$form_state) {
// Not sure the exact email field
if(empty($form['submitted']['mail']['#value'])){
dsm("Should see me now and return to the form for re-submission.");
form_error($form, t('Username or email address already in use.'));
}
}

Answer 3

You could use any validate function here
https://api.drupal.org/api/drupal/includes!form.inc/7
The listed validations would be
date_validate - Validates the date type to prevent invalid dates
(e.g., February 30, 2006).
element_validate_integer -Form element validation handler for
integer elements.
element_validate_integer_positive - Form element validation handler
for integer elements that must be positive
element_validate_number - Form element validation handler for
number elements.
password_confirm_validate - Validates a password_confirm element.
Ex of usage
$form['my_number_field'] = array(
'#type' => 'textfield',
'#title' => t('Number'),
'#default_value' => 0,
'#size' => 20,
'#maxlength' => 128,
'#required' => TRUE,
'#element_validate' => array('element_validate_number')
);

Answer 4

You can use _form_validate().
function my_form_form_validate($form, &$form_state) {
if ((valid_email_address($form_state['values']['field_candid_email'])) === FALSE) {
form_set_error('field_candid_email', t('The email address is not valid.'));
}
if (!(is_numeric($form_state ['values']['field_candid_montant']))) {
form_set_error('field_candid_montant', t('The field value must be numeric.'));
}
}

Answer 5

I changed this line:
$form['submit']['#validate'][] = 'checkout_confirm_email_form_validate'
to this:
$form['actions']['submit']['#validate'][] = 'checkout_confirm_email_form_validate';
And it's works !

Answer 6

Use the following code:
$form['submit']['#validate'][] = 'checkout_confirm_email_form_validate'