How do you copy a PHP object into a different object type

Question

1. New class is a subclass of the original object

2. It needs to be php4 compatible

Answer 1

You can do it with some black magic, although I would seriously question why you have this requirement in the first place. It suggests that there is something severely wrong with your design.

Nonetheless:

function change_class($object, $new_class) {
  preg_match('~^O:[0-9]+:"[^"]+":(.+)$~', serialize($object), $matches);
  return unserialize(sprintf('O:%s:"%s":%s', strlen($new_class), $new_class, $matches[1]));
}

This is subject to the same limitations as serialize in general, which means that references to other objects or resources are lost.