Question

I am studying the differences between Abstract and Interface and I read some sentence
saying

A child class can only extend a single abstract (or any other) class,
whereas an interface can extend or a class can implement multiple
other interfaces.

I understand when he says, “A child class can only extend a single abstract (or any other) class,” he means:

class first
{
    public function Search()
    {
        return 'Hellow';
    }
}

abstract class first2 extends first
{

}

class second extends first2
{   

}

$ob = new second();
echo $ob->Search();

However, I didn’t understand the rest of his sentence, where he says, “whereas an interface can extend or a class can implement multiple other interfaces.”

Could someone please explain his last sentence and add a code example?
Thank you all and have a nice day.

Answer 1

You can implement more than one interface

interface C {
  public function method1();
}

interface D {
  public function method2();
}

class A implements C,D {

   //implement from interface C
   public function method1() {

   }
   //implement from interface D
   public function method2() {

   }
}

Here you will need implement methods from interface C and D. You can also extend interfaces within interfaces, like normal classes.

interface D extends C{}

It’s useful when well you need some common methods. so you write “schema” into interface what methods you are expecting from base class to be implemented.

While abstract is single extended class, you canot create instance for it, only extend. It’s useful when you want have some base class with common functionality or abstract methods what should be implemented later.

More you can always read at php.net – interfaces