Loose comparison vs. strict comparison in PHP

example.php

<?php

class A {
    public $val;
}

class B {
    public $val;
}

class C {
    public $val;
}

echo '
Example 1: 
Compare two objects with properties containing scalar values
';

$a1 = new A;
$a2 = new A;

echo '$a1: ';
var_dump($a1);
echo '$a2: ';
var_dump($a2);

echo '$a1 == $a2: ';
var_dump($a1 == $a2); // true
echo '$a1 === $a2: ';
var_dump($a1 === $a2); // false

echo PHP_EOL;

echo '
Example 2: 
Compare two objects with properties containing scalar values
';

$a1 = new A;
$a2 = new A;

$c1 = new C;
$c1->val = 1;
$a1->b = $c1;

$c2 = new C;
$c2->val = 2;
$a2->b = $c2;

echo '$a1: ';
var_dump($a1);
echo '$a2: ';
var_dump($a2);

echo '$a1 == $a2: ';
var_dump($a1 == $a2); // false
echo '$a1 === $a2: ';
var_dump($a1 === $a2); // false

echo PHP_EOL;

echo '
Example 3: 
Compare two objects with properties containing objects
';

$a1 = new A;
$a2 = new A;

$b1 = new B;
$c1 = new C;
$c1->val = 1;
$b1->val = $c1;
$a1->val = $b1;

$b2 = new B;
$c2 = new C;
$c2->val = 2;
$b2->val = $c2;
$a2->val = $b2;

echo '$a1: ';
var_dump($a1);
echo '$a2: ';
var_dump($a2);

echo '$a1 == $a2: ';
var_dump($a1 == $a2); // false
echo '$a1 === $a2: ';
var_dump($a1 === $a2); // false

echo PHP_EOL;

echo '
Example 4: 
Compare two objects with circular dependencies
';

$a1 = new A;
$a2 = new A;

$b1 = new B;
$a1->val = $b1;
$b1->val = $a1;

$b2 = new B;
$a2->val = $b2;
$b2->val = $a2;

echo '$a1: ';
var_dump($a1);
echo '$a2: ';
var_dump($a2);

// echo '$a1 == $a2: ';
// var_dump($a1 == $a2); // false (fatal error, nesting level too deep)
echo '$a1 === $a2: ';
var_dump($a1 === $a2); // false