Type casting for user defined objects

Question

Just like we do with __ToString, is there a way to define a method for casting?

$obj = (MyClass) $another_class_obj;

Answer 1

Even on PHP 7.2 if you try simple type casting, like so

class One
{
    protected $one = 'one';
}

class Two extends One
{
    public function funcOne()
    {
        echo $this->one;
    }
}


    $foo = new One();
    $foo = (Two) $foo;
    $foo->funcOne();

You'll get error like this

PHP Parse error: syntax error, unexpected '$foo' (T_VARIABLE) in xxx.php on line xxx

So you basically cannot do that, but think again, maybe you wanted only a new function on top of other public functionality of the class?

You can do that using Wrapper

class One
{
    protected $one;
    public function __construct(string $one)
    {
        $this->one = $one;
    }
    public function pub(string $par){
        echo (__CLASS__ . ' - ' . __FUNCTION__ . ' - ' . $this->one . '-' .$par);
    }
}

class Wrapper
{
    private $obj;

    public function __construct(One $obj)
    {
        $this->obj = $obj;
    }
    public function newFunction()
    {
        echo (__CLASS__ . ' - ' . __FUNCTION__);
    }
    public function __call($name, $arguments)
    {
        return call_user_func_array([$this->obj, $name], $arguments);
    }
}

    $foo = new One('one');
    $foo->pub('par1');
    $foo = new Wrapper($foo);
    $foo->pub('par2');
    $foo->newFunction();

One - pub - one-par1

One - pub - one-par2

Wrapper - newFunction

What if you want to get a protected property out?

You can do that too

class One
{
    protected $one;

    public function __construct(string $one)
    {
        $this->one = $one;
    }
}


    $foo = new One('one');
    $tmp = (new class ($foo) extends One {
            protected $obj;
            public function __construct(One $obj)
            {
                $this->obj = $obj;
                parent::__construct('two');
            }
            public function getProtectedOut()
            {
                return $this->obj->one;
            }
        } )->getProtectedOut();

    echo ($tmp);

You'll get

one

And you can get_protected_in the same way