Question

I have a parent class, let’s say class main { ... }, and an extension of it, let’s call it class extension extends main { ... }.

My question is, how would I build another class, called class messages { ... }, which I can use inside the main class and the extended class of main, extension ? Besides the way I know, calling the class messages like this :

$messages = new messages;
$messages->someMethod();

Is there another way without having to do new ... to make the main and extension class inherit the methods inside the messages class ?

Answer 1

AFAIK, PHP does not support multiple inheritance, as others OOP languages do.

So, no, there is NOT another way.

And yes, you should create a property and instantiate the object inside the main class…

class main {
    public $messages;  // may be "protected" or "private" instead

    public __construct()
    {
        $this->messages = new messages();
    }

    public do_something()
    {
        $this->messages->do_something_else();
    }
}

However, there are alternatives to simulate a fake multiple inheritance.

An alternative would be: https://stackoverflow.com/a/356431/370290 – But I don’t recommend this (even the own author doesn’t).

Another alternative: https://stackoverflow.com/a/358562/370290 – IMHO, as weird as the previous one. 🙂

And as of PHP 5.4.0 you can also use traits to achieve a “multiple inheritance” effect: http://php.net/manual/en/language.oop5.traits.php – This is very new at the moment.