OO Extends With A Constructor

[JustinK101]

If I have a base class MyBase:

 

class MyBase {
	public $user_id = NULL;

	 	public function __construct() {
	 		$this->user_id = "justin";
	 	}
  }

 

Then I have a class which inherits the base class MyClass:

 

class Test extends MyBase {
      public static function get_user_id() {
          echo parent::$user_id;
      }
}

 

Finally calling it:

 

    echo Test::get_user_id();

 

First question, do I have to create an instance of MyBase, or when Test extends MyBase will it instanciate it automatically and call the MyBase constructor? Second, I am getting the error:

 

PHP Fatal error:  Access to undeclared static property: MyBase::$user_id

[gizmola]

As long as the child class does not have a constructor the parent constructor will be called.

 

If you're going to try and access a variable statically, it has to be declared to be static.

[JustinK101]

Gizmola,

 

First, who is calling the base constructor?

 

I actually don't want to access user_id statically, but I think to use the keyword `parent` you have to use it like: parent::$user_id. Is there another way to access the property of the MyBase class $user_id from inside the Test class?

[gizmola]

class MyBase {
                public $user_id = NULL;

                public function __construct() {
                        $this->user_id = "justin";
                }
  }

class Test extends MyBase {
      public function get_user_id() {
          echo $this->user_id;
      }
}

$t = new Test();
$t->get_user_id()

[JustinK101]

The only thing, is that I don't want Test to be an instance. It is static. So:

 

class Test extends MyBase {
      public static function get_user_id() {
          echo $this->user_id;
      }
}

 

Obviously, if its static, can't use $this. Is there a way around this?

[gizmola]

You can use "self".  However, php does not have static constructors, so code you put in the parent class constructor will never execute, if that's what you're after.

[ignace]

Why do you want to call it statically? To access $user_id you need to declare it statically.

 

class MyBase {
  protected static $user_id = "justin";
}

class Test extends MyBase {
  public static function get_user_id() {
    return self::$user_id; // or static::$user_id (5.3.x+) or parent::$user_id;
  }
}

print Test::get_user_id();