How to access date value from a datelist form element for validation?

Question

I have a simple form element using datelist as the type. I need to validate this to make sure the date is in the future. But I cannot work out how to access the date itself in the validation method.

Form:

public function buildForm(array $form, FormStateInterface $form_state) {

  $form['date_field'] = array(
    '#title' => $this->t('Expiry'),
    '#type' => 'datelist',
    '#date_part_order' => array('month', 'year'),
    '#date_year_range' => '2017:2027',
    '#date_increment' => 1
  );

  return $form;
}

Validation:

public function validateForm(array &$form, FormStateInterface $form_state) {

  $date_input = $form_state->getValue('date_field');

  if(strtotime(date($date_input)) < strtotime(date('now'))) {  
    $form_state->setErrorByName('date_field', $this->t('The date must be in the future.'));
  }
} 

From the above, $date_input currently returns an object (see below). Essentially, I want to access $date_input->dateTimeObject->date; but doing exactly that will return a fatal error.

Fatal error: Cannot access protected property Drupal\Core\Datetime\DrupalDateTime::$dateTimeObject

$date_input object:

stdClass Object
(
    [__CLASS__] => Drupal\Core\Datetime\DrupalDateTime
    [formatTranslationCache] => 
    [dateParts] => Array
        (
            [0] => year
            [1] => month
            [2] => day
            [3] => hour
            [4] => minute
            [5] => second
        )

    [inputTimeRaw] => 
    [inputTimeAdjusted] => 
    [inputTimeZoneRaw] => 
    [inputTimeZoneAdjusted] => 
    [inputFormatRaw] => 
    [inputFormatAdjusted] => 
    [langcode] => en
    [errors] => Array
        (
        )

    [dateTimeObject] => stdClass Object
        (
            [__CLASS__] => DateTime
            [date] => 2027-12-01T00:00:00+11:00
            [timezone] => Australia/Sydney
        )

    [stringTranslation] => 
)

I could do something like:

$form_state->getValue('date_field')->format('d m Y');

But I suspect there is a better way?

Answer 1

Yes, to compare the date it's better to use the unix timestamp. You can get it by using the method getTimeStamp() and compare it to the current date:

      $value = $form_state->getValue('date_field');
      if ($value->getTimeStamp() > REQUEST_TIME) {
        drupal_set_message('Time is in the future');
      }