Programmatically Validate Form


Drupal 7
Form API
05 Nov 2015


Drupal does not provide a method for validating the submission of a form programmatically. Out of the box, the only way to run validation on a form is to submit the actual form in the UI. This snippet simulates the validation of a form and catches its errors. It does this by:

  1. Building the $form and $form_state array
  2. Running these through custom validation functions
  3. Catching any errors using form_get_errors()
  4. Resetting errors using form_set_error(NULL, NULL, TRUE);


1. Programmatically Validate a Form

Put this in one of your module files. View MODULE_NAME_example_use_callback() for example usage.
 * Simulates validation on a form using defined validation callbacks. It does this by running the validation functions
 * on the $form and $form_state, catching the errors using form_get_errors(), and flushing out the errors using form_set_error()
 * again.
 * @param array $form
 *  The form structure
 * @param array $form_state
 *   The form data
 * @param array $validation_callbacks
 *   An array of validation callbacks to call on the form
 * @return array $errors
 *   An array of errors, or NULL if no errors.
function MODULE_NAME_simulate_form_validation(&$form, &$form_state, $validation_callbacks) {

  foreach ($validation_callbacks as $validation_callback) {
    $validation_callback($form, $form_state);
  // Get errors from the form validation. form_get_errors() retrives them from a static variable
  // set in form_set_error(). form_set_error() would have been called in the validation callbacks
  $errors = form_get_errors();
  // reset the static cache of form_set_error() so the errors won't be picked up on the next call of this function
  $reset_errors = form_set_error(NULL, NULL, TRUE);
  // flush out the messages that were set by form_set_error()
  $messages = drupal_get_messages();
  return $errors;

 * This example will call validation function MODULE_NAME_article_node_form_validate() on the article node form and catch its errors
function MODULE_NAME_example_use_callback() {
  module_load_include('inc', 'node', 'node.pages');
  $node = node_load(1);
  $form = drupal_get_form('article_node_form', $node);
  $form_state['values'] = (array) $node; // cast the node object to an array so it can be used in $form_state['values']
  $validation_callbacks = array('MODULE_NAME_article_node_form_validate'); // your custom validation functions
  $errors = MODULE_NAME_simulate_form_validation($form, $form_state, $validation_callbacks);

  if (!empty($errors)) {
    return FALSE;
  return TRUE;

 * This is just an example validation function. Use your own validation function based on required logic.
 * @param array $form
 *  The form structure
 * @param array $form_state
 *   The form data
function MODULE_NAME_article_node_form_validate(&$form, &$form_state) {
  // This is just an example form validation function.
  if (is_numeric($form_state['values']['title'])) {
    form_set_error('title', t('Please do not enter a number for a title.'));


Placeholder: I'll extend node comments with ajax and other functionality here.