PHP Multi-State Code instance _php instance

Polymorphic definition: Only one interface or base class is concerned, but not the specific class of an object. (same type, different result)

Here are two examples:

First, we found that the base class defines the criteria, and subclasses perform the implementation of the self rule. This is a requirement for polymorphism. At the same time, it is satisfying to rewrite; in fact, this is a different kind of performance; there is no strict satisfaction with an interface, or base class programming. Because you call the time is not Stu->showgrade () but their own methods;

Class stu{public

  function Showgrade () {
    echo ' base class ';  
  }

}


Class Xiaomin extends stu{public

  function Showgrade () {
    echo ' is ' son show ';  
  } 
}

Class Xiaoli extends stu{public

  function Showgrade () {
    echo ' is ' son show ';  
  }

function doit ($obj) {

  if (Get_class ($obj)!= "Stu") {
    $obj->showgrade ();
  }

}

Doit (new Xiaoli ());
Doit (new xiaomin ());

The second example: the Dovoice parameter stipulates the $obj as animal, the consciousness is to accept the implementation class object with the interface. The upward transition. This is consistent with the same type, different results, this is polymorphism;

Actually in Java it would be animal a = new dog (); Because PHP is a type language. There is no object transformation mechanism.

Interface animal{public
  function Voice ();
}

Class Cat implements animal{public
  function voice () {
    echo "miao~~~<br>";
  }
}

Class Dog implements animal{public
  function voice () {
    echo "Wang ~~~<br>";
  }
}

function Dovoice (animal $obj) {
  $obj->voice ();
}


Dovoice (New Dog ());
Dovoice (New Cat ());