Why don't calls to drupal_set_message() show up after a drupal_goto()?

Question

My question is similar to How to redirect the user to a page and show a message on the admin overlay (using drupal_set_message and drupal_goto), but I'm not doing an overlay -- it's just a straight page. This issue has been talked around a bit on this site, but I've never seen a real resolution of it.

My situation is:

• The user submits a form, through the usual method.
• The form has a _submit() handler, which runs: it does some stuff, sets a drupal_set_message(), and then redirects somewhere via drupal_goto().
• The user properly ends up on the intended page, but the message is
  nowhere to be seen.

Any clues on this? I really can't figure out why this is happening.

Answer 1

First of all, keep in mind that drupal_goto() in a form submit handler is bad. The reason is that drupal_goto() shuts down Drupal right after sending the location header, so the rest of your site functionality will not work.

To make a redirect, pass $form_state as reference in your submission handler (FORM_ID_submit($form, &$form_state)), and then set $form_state['redirect'] to where you want to send the user, for example with $form_state['redirect'] = 'node/add';.

Answer 2

I tried in my test site, and the message appears, even using drupal_goto(). I used the following code.

function code_testing_date_form($form, &$form_state) {
  $form['expire'] = array(
    '#type' => 'date_select',
    '#title' => t('Expire Date'),
    '#default_value' => date('Y-m-d H:i:s'),
    '#date_format' => 'Y-H:s',
    '#date_year_range' => '0:+20',
    '#required' => TRUE,
  );

  $form['weight'] = array(
    '#type' => 'weight',
    '#title' => t('Weight'),
    '#description' => t('Optional. In the menu, the heavier items will sink and the lighter items will be positioned nearer the top.'),
    '#default_value' => 5,
    '#delta' => 10,
    '#access' => FALSE,
  );

  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
  );

  return $form;
}

function code_testing_date_form_submit($form, &$form_state) {
  drupal_set_message('You have been redirected.');
  drupal_goto('user');
}

What could cause the issue you are seeing could be:

• There is code that clears the content of $_SESSION['messages'], used to contain the messages set with drupal_set_message().
• There is code that invalidate the current session. In this case, the logged-in user should be logged out.
• You are rendering the form in a template file.

• The template file for the page to which the users are redirected doesn't have code to handle the $messages variable. The default node.tpl.php file contains the following code; if the template doesn't print $messages, the messages set with drupal_set_message() will be not seen.

  <?php if ($breadcrumb): ?>
    <div id="breadcrumb"><?php print $breadcrumb; ?></div>
  <?php endif; ?>
  <?php print $messages; ?>
  <div id="main-wrapper"><div id="main" class="clearfix">