Answer by Alister Bulman for How to initialize static variables

That's too complex to set in the definition. You can set the definition to null though, and then in the constructor, check it, and if it has not been changed - set it:

private static $dates = null;public function __construct(){    if (is_null(self::$dates)) {  // OR if (!is_array(self::$date))         self::$dates = array( /* .... */);    }}