继承和OOP php中的一些属性除外？

Question

Inheritance and except some attribute in OOP php?

I HAVE CLASS A

class A{
    var a;
    var b;
    var c;
    var d;

    function todo1()
      {
            //more code here 
      }
     function todo2()
      {
             //more code here 
      }
     function todo_with_var_c()
      {
             //more code here 
      }

    }

$A_ = new A;

I want get a new object $B the same object of A but except var c todo_with_var_c

So I tried with inheritance in php

class B extends A{

     //TODO
}

$B_ = new $B;//$B_ will the same object  $A_ but except `var c`
and and `todo_with_var_c`

How Can I do it? thanks!

Answer 1

Think about the word extends for a second. It implies the child class is an extension of the parent. Think: more than or special case or "B is an A with added responsibility". This means, you can add stuff, but you should not remove anything. If B is supposed to have less properties, B should be the parent and A the extension, e.g. the other way round.

If you want to hide properties and/or methods in a subclass, use visibility.

class A
{
    protected $a;
    protected $b;
    private $c;
    protected $d;

    public function todo1() { … }
    public function todo2() { … }
    private function todo_with_var_c() { … }
}

Note that I made the properties protected, while in your code they are public because var is old PHP4 syntax (which you should no longer use) when there was no visibility. Properties should not be public though, but accessed through accessors methods (though opinions on that vary).

Further learning resources:

• Learning PHP class
• Importance of protected/private in PHP classes
• Wikipedia: SOLID