What happens if a class doesn't implement all the methods defined in the interface?

When a class is defined to implement an interface, the class must provide definitions of all the methods defined in the interface. Otherwise, you will get compiler time error.

A class must implement all methods of the interface, unless the class is declared as abstract. There are only two choices:

• Implement every method defined by the interface.
• Declare the class as an abstract class, as a result, forces you to subclass the class (and implement the missing methods) before you can create any objects.

interface bird{

   function color();

   function weight();

}

class Bird_class implements bird{

    function color(){

         echo "Color is blue";

    }

    function weight(){

         echo "Weight is 40grms";

    }

}