oop - Why is overriding method parameters a violation of strict standards in PHP?

Question

I know there are a couple of similar questions here in StackOverflow like this question.

Why is overriding method parameters a violation of strict standards in PHP? For instance:

class Foo
{
    public function bar(Array $bar){}
}

class Baz extends Foo
{
    public function bar($bar) {}
}

Strict standards: Declaration of Baz::bar() should be compatible with that of Foo::bar()

In other OOP programming languages you can. Why is it bad in PHP?

Answer 1

In OOP, SOLID stands for Single responsibility, Open-closed, Liskov substitution, Interface segregation and Dependency inversion.

Liskov substitution principle states that, in a computer program, if Bar is a subtype of Foo, then objects of type Foo may be replaced with objects of type Bar without altering any of the desirable properties of that program (correctness, task performed, etc.).

In strong-typed programming languages, when overriding a Foo method, if you change the signature in Bar, you are actually overloading since the original method and the new method are available with different signatures. Since PHP is weak typed, this is not possible to achieve, because the compiler can't know which of the methods you are actually calling. (hence the reason you can't have 2 methods with the same name, even if their signatures are different).

So, to avoid the violation of Liskov Substituition principle, a strict standard warning is issued, telling the programmer something might break due to the change of the method signature in the child class.