Question

i am learning about the difference between abstract classes and interfaces,
but theoretical explanations are hard to understand when you don’t have practical example.
i have read that:
By updating the base class, all inheriting classes are automatically updated with the change. Interfaces, on the other hand, cannot be changed once created. If a new version of an interface is required, you must create a whole new interface.
if can someone please supply me an practical example for this lines i will be very thankful,
Wishing you a pleasant week.

Answer 1

Consider this example. We have a drivable interface, automobile abstract, and a Pinto class that uses both.

interface Drivable 
{
  public function go();
}

abstract class Automobile 
{
  public $type;

  public function getType() {
    return $this->type;
  }
}

class Pinto
    extends Automobile
    implements Drivable 
{
  public function go() {
    // code to make it go
  }
}

We can easily add methods to all automobiles by defining them in Automobile. Any new method added there will be available to all extending classes.

However, if we add a method to the Drivable interface, we must seek out and implement said method in every class that implements it to add the new method or else it won’t compile.

For example, say we add a stop() method to our interface. Pinto will immediately raise errors because it doesn’t have a stop method.