Description:
------------
Hopefully the test script is self-explanatory. When running array_intersect on arrays that contains an object that mutates itself and the return value in its __toString() method, the result is an empty array even if there are literal values in the arrays that intersect.

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

class A {
	protected $i = 0;

	public function __toString() {
		$this->i++;
		return "$this->i";
	}
}

$a = new A;

$b = ['100', $a];

var_dump(array_intersect($b, $b));


Expected result:
----------------
array(1) {
  [0]=>
  string(3) "100"
}


Actual result:
--------------
array(0) {
}