Using object property as default for method property

Question

I'm trying to do this (which produces an unexpected T_VARIABLE error):

public function createShipment($startZip, $endZip, $weight =  $this->getDefaultWeight()){} 

I don't want to put a magic number in there for weight since the object I am using has a "defaultWeight" parameter that all new shipments get if you don't specify a weight. I can't put the defaultWeight in the shipment itself, because it changes from shipment group to shipment group. Is there a better way to do it than the following?

public function createShipment($startZip, $endZip, weight = 0){     if($weight <= 0){         $weight = $this->getDefaultWeight();     } } 

Answer 1

This isn't much better:

public function createShipment($startZip, $endZip, $weight=null){     $weight = !$weight ? $this->getDefaultWeight() : $weight; }  // or...  public function createShipment($startZip, $endZip, $weight=null){     if ( !$weight )         $weight = $this->getDefaultWeight(); }