/**
* Returns day of week for a given date (0 = Sunday).
*
* @param mixed $date
* (optional) A date object, timestamp, or a date string.
* Defaults to NULL, which means use the current date.
*
* @return int
* The number of the day in the week.
*/
public static function dayOfWeek($date = NULL)
{
if (!$date instanceof DrupalDateTime) {
$date = new DrupalDateTime($date);
}
if (!$date->hasErrors()) {
return $date->format('w');
}
return NULL;
}
