Description:
------------
There is currently no way to portably write this:

class myTime extends DateTime {
  public static function createFromFormat($format, $time, DateTimeZone $tz = null) { }
}

such that it doesn't generate a warning in PHP 5 and or PHP 7. Without "DateTimeZone $tz" it gives:

Warning: Declaration of myTime::createFromFormat() should be compatible with DateTime::createFromFormat($format, $time, DateTimeZone $object = NULL) in /home/rasmus/cc on line 0

in PHP 7 and with it we get:

Strict Standards: Declaration of myTime::createFromFormat() should be compatible with DateTime::createFromFormat($format, $time, $object = NULL) in /home/rasmus/cc on line 4

in PHP 5.6. We need a sensible upgrade path here which is probably to just simply drop the DateTimeZone restriction from the prototype.