Check if form failed validation - drupal

Question

I added a validation hook to a node creation form.
For my project, i need this validation only ONE time: basically i just check if a value already exists in the DB and i notify it to the user. If the user still submits the form, i must add it anyway.
i would like to do something like that:
if (form_did_not_fail_validation_before) {
$form['#validate'][] = 'my_module_validation_hook';
}
in my hook_form_alter, so that validation hook is only called the first time.
I can't find a way to check if the form already failed validation, any ideas?

Answer 1

Here is one way of solving this issue your issue. But if you using some form input like text form I suggest that you use Ajax callback since it will feel more dynamic. Let me know if you want an example of how to solve it with Ajax callback?
I guess the key here is that I use $form_state['rebuild'] = true; so that form is rebuilt and than it easy to get the value from the $form_state['values']
Here is the code:
function example_form(array $form, array &$form_state)
{
$form['temp'] = array(
'#type' => 'value',
'#value' => array_key_exists('values', $form_state) ? $form_state['values']['temp'] + 1 : 1,
);
if (array_key_exists('values', $form_state) && $form_state['values']['temp'] == 1)
{
$form['message'] = array(
'#markup' => t('I only give you one warning'),
'#prefix' => '<p>',
'#suffix' => '</p>',
);
}
$form['submit_button'] = array(
'#type' => 'submit',
'#value' => t('Click Here!'),
);
return $form;
}
function example_form_validate(array $form, array &$form_state)
{
$form_state['rebuild'] = true;
}
function example_form_submit(array $form, array &$form_state)
{
if($form_state['values']['temp'] == 1) {
// I will not store anything
} else {
// now I will store it :)
}
}