Sams Teach Yourself PHP in 24 Hours, Third Edition

Passing and Assigning Objects

Before we leave the subject of PHP and objects, it is important to stress a particular difference between PHP 4 and PHP 5. In PHP 4, objects were passed to and from functions by value. Let’s pass an object around a bit to test this process:

class PassObj {
  function PassObj( $item ) {
    $item->name="harry";
  }
}

class Item {
  var $name = "bob";
}

$item = new Item();
$pass = new PassObj( $item );
print $item->name;

The PassObj class in the fragment has a constructor that accepts an Item object. It changes the $name property of the Item object and does nothing else. If we were to run this code with PHP 4, a copy of an Item object would be passed to the PassObj constructor. The original object would not be affected by ...