Inheritance & method params PHP

Question

Let say I have a PHP Class:

class MyClass {
   public function doSomething() {
     // do somthing
   }
}

and then I extend that class and override the doSomething method

class MyOtherClass extends MyClass {
   public function doSomething() {
     // do somthing
   }
}

Q: Is it bad practice to change, add and or remove method params? e.g:

class MyOtherClass extends MyClass {
   public function doSomething($newParam) {
     // do somthing
     // do something extra with $newParam
   }
}

Thanks

Answer 1

In general, yes it is bad design. It breaks the design's adherence to the OOP principle of polymorphism (or at least weakens it)... which means that consumers of the parent interface will not be able to treat instances of your child class exactly as they would be able to treat instances of the parent.

Best thing to do is make a new semantically named method (semantic in this case meaning that it conveys a similar meaning to the original, with some hint as to what the param is for) which either calls the original, or else in your overridden implementation of the original method, call your new one with a sensible default.

class MyOtherClass extends MyClass {
   public function doSomething() {
     return $this->doSomethingWithOptions(self::$soSomethingDefaultOptions);
   }

   public function doSomethingWithOptions($optsParam) {
     parent::doSomething();
     // ...
   }
}