Display blank date in hook_form

Question

I am creating a custom page with hook_form and using the datatype '#type' => 'date,

I would like to make that field required.

AND, I want it to initially display blank.

Without #default_value specified, the default is today. How do I, in effect, make the default_value NULL?

Answer 1

You can use a #pre_render function on that field to unset the values and add an empty option on the 3 select boxes.

$form['start_date'] = array(
    '#type' => 'date',
    '#title' => t('Date'),
    '#description' => t('Your field description ...'),
    '#required' => true,
    '#pre_render' => array('_YOUR_MODULE_form_pre_render_date'),
);

function _YOUR_MODULE_form_pre_render_date(&$element)
{
    // Don't put empty values if a date has already been set
    if (date('Ynj') !== implode('', array_values($element['#default_value']))) {
        return $element;
    }

    // Loop through each field, add empty option and unset value
    foreach (array('year', 'month', 'day') as $field) {
        if (!isset($element[$field])) {
            continue;
        }

        unset($element[$field]['#value']);
        $element[$field]['#default_value'] = '0';
        $element[$field]['#options'] = array(
            '0' => '',
        ) + $element[$field]['#options'];
    }

    return $element;
}

Answer 2

As I was having date validation problems using Mike Vranckx answer above, I needed to implement a custom validation method to get around the The specified date is invalid. error.

First add a custom #element_validate function to the form element:

  $form['dob'] = array(
    '#type' => 'date',
    '#title' => t('Date Of Birth'),
    '#weight' => 9,
    '#pre_render' => array(
      '_form_date_empty',
    ),
    '#element_validate' => array('_form_date_empty_validate'),
  );

However it seems that setting this value will prevent the default date_validate() function from running, which still has some value, we just want to make sure it doesn't prevent blank dates:

function _form_date_empty_validate($element, &$form_state, $form) {
  $date = $element['#value'];
  if (($date['year'] || $date['month'] || $date['day'])) {
    date_validate($element, $form_state, $form);
  }
}