在PHP中自定义类型提示

Question

I'm writing a custom extension system for php, which allows for defining a class with new function for an existing class, and add said functions to a class after its defined.

As said, extensions are written as a separate class, lets call one MyExtension , and lets say that this extension extends upon to existing classes, MyExtendedClass1 and MyExtendedClass2 . So MyExtension adds some functions to MyExtendedClass1 AND MyExtendedClass2 .

What I want to do is allow users to type hint base on MyExtension.

// $object is guaranteed to either be an instance of MyExtension
// or be a class that is extended with MyExtension
function someFunction(MyExtension $object) {

}
$post = new MyExtendedClass1(); // Is extended by MyExtension
someFunction($post);

$post = new MyExtendedClass2(); // Is extended by MyExtension
someFunction($post);

What I'm wondering is:

Is there any way to "add a type to an object"? Is there any way I can trick the type checking to allow these calls.

Answer 1

It's hard to understand your question because you need custom extension descibed as customly extended object.

If you need some_function to operate on different types it can't use them directly and type hint can't determine concrete type - use interface .

Your types need to be extended with functionality of common interface that function can depend on - use wrapper objects that implement same inteface, but know (how to communicate) the concrete type.

interface MyExtensionInteface {
    public function doSoemthingSpecial();
}

function some_function(MyExtensionInterface $myExtension) {
    $myExtension->doSomethingSpecial();
}

class MyExtensionOfExtendedClass1 implements MyExtensionInteface
{
    public function __construct(MyExtendedClass1 $obj) {
        $this->extended = $obj;
    }

    public function doSomethingSpecial() {
        //...with MyExtendedClass1 type
    }
}

class MyExtensionOfExtendedClass2 impements MyExtensionInterface
{
     public function __construct(MyExtendedClass2 $obj) {
         $this->extended = $obj
     }

     public function doSomethingSpecial() {
         //...with MyExtendedClass2 type
     }
}

$a = new MyExtensionOfExtendedClass1(new MyExtendedClass1());
some_function($a);

$b = new MyExtensionOfExtendedClass2(new MyExtendedClass2());
some_function($b);

"Extension" naming is for question context only - it should have real object meaning. For example: DuckSoup(Duck) + ChickenSoup(Chicken) + function:cook(Soup)