Ajax callback works only once

Question

I am using Drupal 7. I want to rebuild a part of form when a button is clicked. My form looks like this:

$form['me'] = array(
    '#type' => 'fieldset',
    '#value' => t('name'),
    '#prefix' => '<div id="me-wrapper>',
    '#suffix' => '</div>'
);

It contains various text fields and a submit button. The submit button looks like

$form['me']['save'] = array(
    '#type' => 'submit',
    '#validate' => array('save_validate'),
    '#submit' => array('save_submit'),
    '#ajax' => array(
        'wrapper' => 'me-wrapper',
        'callback' => 'me_ajax_callback'
    ),
);

in the save_submit function I set $form_state['rebuild] = true;

in ajax callback function

function me_ajax_callback($form, $form_state) {
    return $form['me'];
}

Now, what happens is first time when I click submit, the ajax returns data and replaces the wrapper. But, 2nd time when I do so, I get a POST Internal Server Error 500.

Looking around the Form API, I set $form_state['no_cache']=true; in submit handler and that prevents the POST error but still the AJAX response is empty.

It works fine if, I reload the page. So, in short, the first time I hit submit I get an AJAX response. On the second time, the response is blank.

Answer 1

Ok, I have solved the issue and this might help someone in future. I was dealing with a form which was actually a collection of various small forms. Each small form had various text fields and submit handler. So, when reloading a small form using AJAX I was setting $form_state['rebuild'] = true, this in process rebuilt the whole form in the back. But AJAX callback only rendered a small part of form into the wrapper. So, when I pressed the button again there was post error as Drupal was expecting values in new rendered form whereas it got a mixture of Old and new form. It happens because Drupal while rendering a form into HTML adds id to it, e.g., id = edit-save but when we rebuild it without reloading the page, it changes to something like id = edit-save--2 and which keeps on to increment every time it's rebuilt. So, if your form needs rebuilding, reload the whole form else set $form_state['rebuild'] = false and that should allow subsequent AJAX calls without any post error.