Do classes which extend other classes inherit the same constructor?

For instance...

if I have a Module class:

class Module{

  var $page;

  function Module($page){
    $this->page = $page;
  }
}

and then a specific Ne开发者_如何转开发ws module class:

class News extends Module {
  function aFunction(){
    return $this->page->id;
  }
}

can I instantiate News like this:

$page = new Page();
$news = new News($page);

or would I have to do this:

$page = new Page();
$news = new News();
$news->page = $page;

Thank you.

PS: I'm quite new to OOP php, so bear with me lol. I've gone from procedural php to objective-c and now back to objective php. :p Its very difficult trying to compare each to the other.

---

Yes, they inherit the constructor. This is something you can easily test yourself. For instance:

class Foo {
  function __construct() {
    echo "foo\n";
  }
}

class Bar extends Foo {
}

When you run:

$bar = new Bar();  // echoes foo

However, if you define a custom constructor for your class, it will not call Foo's constructor. Make sure to call parent::__construct() in that case.

class Baz extends Foo {
  function __construct() {
    echo "baz ";
    parent::__construct();
  }
}

$baz = new Baz();  // echoes baz foo

All of this is true for your old-style constructors, too (name of class vs __construct).

---

One solution would be to specify a constructor for News, function News($page) {...} which would call the parent constructor like this: parent::Module($page). You're trying to encapsulate $page, and accessing it directly defeats this purpose.

---

I'm not familiar with PHP, but the last piece of code would look very bizarre in any OOP language I know. In OOP languages the constructor of News would implicitly or explicitly call the constructor of Module.

---

First off, you should use __construct() instead of the name of the class as the constructor as this is more modular.

As with any other OOP language, the constructor of a child class is inherited by its parent, so your first example will indeed work.

One thing to keep in mind, though, is that a parent constructor is not implicitly called by the parent. So if you define a constructor in News, the first example won't work anymore unless you have the News constructor handle $page on its own, or call parent::__construct($page);

Another issue is that the encapsulation the classes provide is violated by $page being public. The var keyword is a remnant of PHP 4, and you should declare $page as private. It should be visible to and handled by only the Module class. For instance, why does News need aFunction?

---

you can inherit the attributs of another class for example the italienChef inherited the makeChiken from the class Chef so when we run it it gives us // the chef makes chiken

class Chef{

    function makeChiken(){
        echo "the chef makes chiken <br>";
    }
}

class ItalienChef extends Chef{
   function makePasta(){
    echo "the chef makes pasta";
   }
   
$italienchef = new ItalienChef();
$italienchef-> makeChiken();