Description:
------------
When I compare two obejcts from two different but identially-looking classes then the comparison operators yield contradicting results.

In the samle code below, there are two variables $a and $b which are not in ==, nor in === nor in <= nor in >= relationship.

Moreover, the spaceship operator tells that $a>$b and $b>$a as well. 

Test script:
---------------
	error_reporting(E_ALL);
	
	class Objy_1 {
		public $v =1;
	}
	
	class Objy_2 {
		public $v =2;
	}

	$a = new Objy_1();
	$b = new Objy_2();
	
	var_dump($a < $b);    // false
	var_dump($a > $b);    // false
	var_dump($a == $b);   // false
	var_dump($a === $b);  // false
	var_dump($a <=> $b);  // false
	var_dump($a <=> $b);  // 1 which means $a > $b
	var_dump($b <=> $a);  // 1 which means $b > $a


Expected result:
----------------
I would expect non-contradicting results. In this concrete cases, I think $a == $b should be true, $a <=> $b and $b <=> $a should be 0.

Moreover, I think it would be nice to get a warning if I want to compare objects from different classes.