Description:
------------
I do not understand if is an error or not, but iterating over arrays with complex objects is slower than iterate over arrays made with more simple objects. 

In some case (but i can't reproduce it), iterate over arrays with 100 elements is 100x slower than iterate other array made of 100 simpler objects.

(sorry for my English)

Test script:
---------------
<?php

// create some arrays

 // integer array (1000 items)
$vals = range(0,1000);

// simple object array (1000 items)
$obj = array_map(function($v){ 
	$o = new stdClass();
	$o->v = $v;
	return $o; 
}, $vals);

// more complex object array (1000 items)
$objs = array_map(function($v)use(&$obj){ 
	$o = new stdClass();
	$o->res = array();
	for ($i = 0; $i<500; $i++){
		$o->res[$i] = $obj[$i];
	}
	for (true; $i<1000; $i++){
		$o->{'res'.$i} = $obj[$i];
	}
	return $o; 
}, $vals);

// TESTS

// 1. loop over integer array 
// 1000000 iterations
$t = microtime(1);
foreach ($vals as $o1){
	foreach ($vals as $o2){
	}
}
echo microtime(1)-$t."\n";

// 2. loop over simple object array 
// 1000000 iterations 
// 15% slower than loop n.1
$t = microtime(1);
foreach ($obj as $o1){
	foreach ($obj as $o2){
	}
}
echo microtime(1)-$t."\n";

// 3. loop over complex object array 
// 1000000 iterations
// 50% slower than loop n.1
$t = microtime(1);
foreach ($objs as $o1){
	foreach ($objs as $o2){
	}
}
echo microtime(1)-$t."\n";


Expected result:
----------------
all loop  should take the same amount of time. (at most with slight differences)


Actual result:
--------------
loop n.3 is 50% slower than loop 1
loop n.3 is 30% slower than loop 2
in some case iterate over complex array can be 100x slower