function form_set_error

Files an error against a form element.

When a validation error is detected, the validator calls form_set_error() to indicate which element needs to be changed and provide an error message. This causes the Form API to not execute the form submit handlers, and instead to re-display the form to the user with the corresponding elements rendered with an 'error' CSS class (shown as red by default).

The standard form_set_error() behavior can be changed if a button provides the #limit_validation_errors property. Multistep forms not wanting to validate the whole form can set #limit_validation_errors on buttons to limit validation errors to only certain elements. For example, pressing the "Previous" button in a multistep form should not fire validation errors just because the current step has invalid values. If #limit_validation_errors is set on a clicked button, the button must also define a #submit property (may be set to an empty array). Any #submit handlers will be executed even if there is invalid input, so extreme care should be taken with respect to any actions taken by them. This is typically not a problem with buttons like "Previous" or "Add more" that do not invoke persistent storage of the submitted form values. Do not use the #limit_validation_errors property on buttons that trigger saving of form values to the database.

The #limit_validation_errors property is a list of "sections" within $form_state['values'] that must contain valid values. Each "section" is an array with the ordered set of keys needed to reach that part of $form_state['values'] (i.e., the #parents property of the element).

Example 1: Allow the "Previous" button to function, regardless of whether any user input is valid.

$form['actions']['previous'] = array(
  '#type' => 'submit',
  '#value' => t('Previous'),
  '#limit_validation_errors' => array(),
  // No validation.
  '#submit' => array(
    'some_submit_function',
  ),
);

Example 2: Require some, but not all, user input to be valid to process the submission of a "Previous" button.

$form['actions']['previous'] = array(
  '#type' => 'submit',
  '#value' => t('Previous'),
  '#limit_validation_errors' => array(
    array(
      'step1',
    ),
    // Validate $form_state['values']['step1'].
    array(
      'foo',
      'bar',
    ),
  ),
  '#submit' => array(
    'some_submit_function',
  ),
);

This will require $form_state['values']['step1'] and everything within it (for example, $form_state['values']['step1']['choice']) to be valid, so calls to form_set_error('step1', $message) or form_set_error('step1][choice', $message) will prevent the submit handlers from running, and result in the error message being displayed to the user. However, calls to form_set_error('step2', $message) and form_set_error('step2][groupX][choiceY', $message) will be suppressed, resulting in the message not being displayed to the user, and the submit handlers will run despite $form_state['values']['step2'] and $form_state['values']['step2']['groupX']['choiceY'] containing invalid values. Errors for an invalid $form_state['values']['foo'] will be suppressed, but errors flagging invalid values for $form_state['values']['foo']['bar'] and everything within it will be flagged and submission prevented.

Partial form validation is implemented by suppressing errors rather than by skipping the input processing and validation steps entirely, because some forms have button-level submit handlers that call Drupal API functions that assume that certain data exists within $form_state['values'], and while not doing anything with that data that requires it to be valid, PHP errors would be triggered if the input processing and validation steps were fully skipped.

Parameters

$name: The name of the form element. If the #parents property of your form element is array('foo', 'bar', 'baz') then you may set an error on 'foo' or 'foo][bar][baz'. Setting an error on 'foo' sets an error for every element where the #parents array starts with 'foo'.

$message: The error message to present to the user.

$limit_validation_errors: Internal use only. The #limit_validation_errors property of the clicked button, if it exists.

Return value

Return value is for internal use only. To get a list of errors, use form_get_errors() or form_get_error().

See also

http://drupal.org/node/370537

http://drupal.org/node/763376

Related topics

File

drupal/core/includes/form.inc, line 1641

Functions for form and batch generation and processing.

Code

function form_set_error($name = NULL, $message = '', $limit_validation_errors = NULL) {
  $form =& drupal_static(__FUNCTION__, array());
  $sections =& drupal_static(__FUNCTION__ . ':limit_validation_errors');
  if (isset($limit_validation_errors)) {
    $sections = $limit_validation_errors;
  }
  if (isset($name) && !isset($form[$name])) {
    $record = TRUE;
    if (isset($sections)) {

      // #limit_validation_errors is an array of "sections" within which user
      // input must be valid. If the element is within one of these sections,
      // the error must be recorded. Otherwise, it can be suppressed.
      // #limit_validation_errors can be an empty array, in which case all
      // errors are suppressed. For example, a "Previous" button might want its
      // submit action to be triggered even if none of the submitted values are
      // valid.
      $record = FALSE;
      foreach ($sections as $section) {

        // Exploding by '][' reconstructs the element's #parents. If the
        // reconstructed #parents begin with the same keys as the specified
        // section, then the element's values are within the part of
        // $form_state['values'] that the clicked button requires to be valid,
        // so errors for this element must be recorded. As the exploded array
        // will all be strings, we need to cast every value of the section
        // array to string.
        if (array_slice(explode('][', $name), 0, count($section)) === array_map('strval', $section)) {
          $record = TRUE;
          break;
        }
      }
    }
    if ($record) {
      $form[$name] = $message;
      if ($message) {
        drupal_set_message($message, 'error');
      }
    }
  }
  return $form;
}