unserialize

spl_autoload_register(function ($class) {
    var_dump("autoload: $class");
});

/**
class Foo
{
    public function __construct()
    {
        var_dump('called Foo::__construct');
    }
}

$foo = new Foo();
var_dump(serialize($foo));
*/

$serialized = 'O:3:"Foo":0:{}';
$foo = unserialize($serialized, ['allowed_classes' => false]);
var_dump($foo);

/**
class __PHP_Incomplete_Class#2 (1) {
    public $__PHP_Incomplete_Class_Name =>
    string(3) "Foo"
}
*/