如何使用PHP类扩展？

Question

QUESTION :

I Cannot figure how to use classes extends in PHP... Even reading php.net website and some examples, there is something I cannot understand or missing !

Can you please tell me what I'm doing wrong ?

Api.php

class Api
{

    public static $action = '';


#    public function __construct()
#    {
#    }

    public function actionCaller ($action,$args=NULL)
    {
        return self::$action_($args);
    }
}

ApiForum.php

class ApiForum extends Api
{

    #private static $forum;

    public function __construct()
    {
        #self::$forum = new Api();
    }

    private function getPost ($args)
    {
        echo 'executed.';
        #return "get forum post $args";
    }

}

test.php

<?php
error_reporting(E_ALL);
ini_set('display_errors', true);


require_once('config.php');
require_once('classes/_Autoload_.php');


echo Api::actionCaller('forum')->getPost();

The result :

PHP Fatal error:  Call to a member function getPost() on a non-object in /var/www/html/api.example.com/test.php on line 10

Please be clement with me ;)

CL

ANSWER:

Okay it's working now ! Thanks to all... There was more than one problem, here is the result :

Api.php

class Api
{

#    public function __construct()
#    {
#    }


    public function actionCaller ($action,$args=NULL)
    {
        return self::$action($args);
    }

    public function forum ()
    {
        return new ApiForum();
    }


}

ApiForum.php

class ApiForum extends Api
{

#    public function __construct()
#    {
#    }



    public static function getPost ($args)
    {
        echo 'executed.';
    }

}

test.php

error_reporting(E_ALL);
ini_set('display_errors', true);


require_once('config.php');
require_once('classes/_Autoload_.php');


echo Api::actionCaller('forum')->getPost('test');

I feel I need some more readings about classes and objects scopes ... :)

Answer 1

Just switch your "getPost" method declaration for this:

static function getPost($args){

A private method means only that class can execute that method. A static method means that it can be called without an object being instantiated, like what you're trying to do with the double colon eg. class::method(args) .

Just for completeness sake, a public function is the middle ground. An object has to be instantiated for you to call it (via $object->method(args) ), but it is available to any file that has imported that class

EDIT

Just a side note: I'd also like to add that for a method to be used as a static method, it still needs to be "included"! I apologise for the use of the word "imported", I've been playing around in a lot of other languages recently!