Upgrading scripts to conform to PHP 4.4 ref. implementation

[pachanga]

Folks, is there any PHP 4.4 upgrading paper? There's very nice PHP 5.1 upgrading manual but i couldn't find anything on PHP 4.4 while its new reference implementation breaks tons of existing scripts.

Basically, all return/pass by reference calls should be changed. e.g the following code:

function &Foo($id) {
   if(isset($arr[$id]))
     return $arr[$id];
} 

becomes:

function &Foo($id) {
   if(isset($arr[$id]))
     return $arr[$id];

   $zref = null;
   return $zref;
} 

But i wonder why this triggers a notice then:

function &Foo($id) {
   if(isset($arr[$id]))
     return $arr[$id];

   return $zref = null;
} 

At the same time the following code works just fine:

function foo(&$arr) {
  $arr[] = 3;
}

foo($arr = array(1, 2)); 

And in the following case "return parent :: foo()" in Bar::foo() shouldn't be changed:

class Foo {
  var $ref = 1;
  function & foo() {
    return $this->ref;
  }
}

class Bar extends Foo {
  function & foo() {
    return parent :: foo();
  }
} 

Which means, i guess, that if the function declared with & and returns reference, there's no need in temporary variable when returning its result.

Any other issues like those i mentioned?