CODEWITHSUNDEEP
phpc++polymorphism
user7681202
user7681202

Reputation: 141

Is it called Polymorphism when not using a parent class in PHP?

In C++, if I want to use Polymorphism, I would create a parent class and then derive many child classes from the parent class, and then I would be able to assign an address of a child class object to a pointer variable of the parent class.

For example: say that I have a parent class called Animal, and then I derived two child classes from Animal, which are Dog and Cat, and the three classes have a method called speak().

Now I can create a function that takes Animal* as argument:

void foo(Animal* animal)
{
    animal->speak();
}

And do the following:

Cat *cat = new Cat();
Dog *dog = new Dog();
foo(cat);
foo(dog);

But in PHP, a variable can be of any type, so even if I don't have a parent Animal class and only have a Cat and a Dog class, I can still do the following:

function foo($animal)
{
    $animal->speak();
}

$cat = new Cat();
$dog = new Dog();
foo($cat);
foo($dog);

So is it still called Polymorphism when not using a parent class?

Upvotes: 0

Views: 180

Answers (2)

Useless
Useless

Reputation: 67723

The sort of polymorphism you're describing in C++ is subtyping (the third in the list of three distinct meanings in this linked Wikipedia article).

This is also described (at least in statically-typed languages like C++) as dynamic polymorphism since the point is that the "dynamic" (runtime) type of your object varies from the "static" compile-time type of the interface.

What you're discussing in PHP is duck typing, which is essentially a form of parametric polymorphism.

This is roughly equivalent to the static polymorphism you get from templates in C++, although the implementation is obviously very different.

Upvotes: 1

Ulrich Eckhardt
Ulrich Eckhardt

Reputation: 17415

Polymorphism is a concept that's pretty abstract and in particular independent of any particular implementation. In that sense, yes, your code uses polymorphism.

Now, concerning your comparison with C++, you are comparing apples with oranges here. The following piece of PHP is much closer to the C++ code:

function foo(Animal $animal)
{
    $animal->speak();
}

On the other hand, you can also adjust the C++ code:

template<typename animal_type>
void foo(animal_type& animal)
{
    animal.speak();
}

Note that I have fixed the non-idiomatic use of pointers by your version, but the important part is that the function is now a template.

Upvotes: 0

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