Question

Is it possible to declare an instance of a class as a property in PHP?

Basically what I want to achieve is:

abstract class ClassA() 
{
  static $property = new ClassB();
}

Well, I know I can’t do that, but is there any workaround beside always doing something like this:

if (!isset(ClassA::$property)) ClassA::$property = new ClassB();

Answer 1

you can use a singleton like implementation:

<?php
class ClassA {

    private static $instance;

    public static function getInstance() {

        if (!isset(self::$instance)) {
            self::$instance = new ClassB();
        }

        return self::$instance;
    }
}
?>

then you can reference the instance with:

ClassA::getInstance()->someClassBMethod();