Can I change the access modifiers of any parent function in Child class?
Child classes may only "loosen" the visibility, e.g.
class ParentClass
{
protected function foo() {}
}
can be
class ChildClass extends ParentClass
{
public function foo() {}
}
but not
class ChildClass extends ParentClass
{
private function foo() {}
}
Apart from that, you can use the Reflection API to change Visibility at runtime:
though you should ask yourself why you would want to do that. Usually parent classes that hide methods or properties from their children do so for a reason.
No. It is impossible. And not only in PHP.
My own tests suggest that a child class can increase the visibility but not decrease it.
For example, suppose a parent class has a member variable declared as private. Then a child class can define the same member variable as either private, protected, orpublic`.
Similarly, if the parent member is declared as protected, then the child can can declare the member as protected or public.
Finally, if the parent declares the member as public, then the member must be public in all children.