>> Shutdown functions and object destructors will always be executed even if exit is called.

It is false if you call exit into desctructor.

Normal exit:
<?php
class A
{
    public function __destruct()
    {
        echo "bye A\n";
    }
}

class B
{
    public function __destruct()
    {
        echo "bye B\n";
    }
}

$a = new A;
$b = new B;
exit;

// Output:
// bye B
// bye A
?>

// Exit into desctructor:
<?php
class A
{
    public function __destruct()
    {
        echo "bye A\n";
    }
}

class B
{
    public function __destruct()
    {
        echo "bye B\n";
        exit;
    }
}

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

// Output:
// bye B
?>