in_array() related problem

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Hello all,

I'm new to this list. To not flooding the bug tracking system I hope
to clarify some of my understanding here.

I am referring to the (now bogus) bug report
http://bugs.php.net/bug.php?id=39356&edit=2. This happens after my
upgrade to PHP 5.2, where the code shown produces a "Fatal error:
Nesting level too deep - recursive dependency?". Same testing code
reproduced below:

----------------------------
<?php
class A
{
	public $b;
}

class B
{
	public $a;
}

$a = new A;
$b = new B;
$b->a = $a;
$a->b = $b;

$test = array($a, $b);

var_dump(in_array($a, $test));
----------------------------

I think this is not rare for a child item to have knowledge about its
parent, forming a cross-reference.

This code runs with no problem in PHP5.1.6, but not in 5.2. Ilia
kindly points out that "In php 5 objects are passed by reference, so
your code does in
fact create a circular dependency.". I know the passed by reference
rule. What I'm now puzzled is, why this should lead to an error.

To my knowledge, despite the type-casting issue and actual algorithm,
in_array() should actually do nothing more than:

function mimic_in_array($search, $list)
{
 foreach ($list as $item)
   if ($search == $item)
     return true;
 return false;
}

Which means:
1. in_array() isn't multi-dimensional.
2. in_array() doesn't care about the properties of any object.

That is, I don't expect in_array() to nest through all available inner
arrays for a match, not to mention those are object properties, not
arrays.

So here is the question: Why should in_array() throws such a "Fatal
error: Nesting level too deep" error? Why should it care? Is there any
behaviour I don't know?

Thanks all in advance.

Tamcy

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