How can I tell what values have changed in a validate hook of a form submission?

2 Answers 2


What I have done is to see if the value in $form_state['values'] is different from the #default_value in $form, like so:

if ( $form_state['values']['variable'] <> $form['variable']['#default_value'] ) { ... }
  • kinda what i said above, no?
    – au_stan
    May 8, 2012 at 17:16
  • Couldn't tell -- it seemed like only a flag to indicate that a change had occurred? I wanted more granularity.
    – user1359
    May 8, 2012 at 17:57

Something that i do in my forms is set defaults.


    isset($form_state['values']['datacenter']) ?
    $selected = $form_state['values']['datacenter'] : $selected = 0;

$form['grid']['datacenter'] = array(
    '#title'            => 'Datacenter',
    '#type'             => 'radios',
    '#default_value'    => $selected,
    '#required'         => true,
    '#options'          => array(),                     

what you could do is check your #default_value to see if its not 0 in this case. so in your MYMODULE_form_validate($form, &$form_state) function, simply grab your $form_state values and if its not zero in this case, call some other function or whatever you want to do.

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