Trying to access properties of the containing obje

Question

After hours looking for solutions and patterns, it's time for me to ask the pros.

I'd love to order my object in a logical hierarchy, but still want to be able to access properties of the parent object. A simple example how I'd love to have it work...

    class car {

       public $strType;  // holds a string
       public $engine;   // holds the instance of another class

       public function __construct(){
           $this->type = "Saab";
           // Trying to pass on $this to make it accessible in $this->engine
           $this->engine = new engine($this);
       }

    }

    class engine {

        public $car;

        public function __construct($parent){
            $this->car = $parent;
        } 

        public function start(){
            // Here is where I'd love to have access to car properties and methods...
            echo $this->car->$strType;
        }
    }

    $myCar = new car();
    $myCar->engine->start();

What I won't achieve is that a method in engine can access the 'parent' car properties. I managed to do so like this, but I believe that is very very ugly...

    $myCar = new car();
    $myCar->addParent($myCar);

From within the addParent MethodI would be able to pass the instance on to the engine object. But that can't be the clue, can it? Is my whole idea queer?

I don't want engine to inherit from car because a car has lots of methods and properties and engine has not. Hope you get what I mean.

Hoping for hints, Cheers Boris

Answer 1

As @Wrikken mentioned, the correct syntax would be echo $this->car->strType;

type does not seem to be a member of car, but if you changed it the line to

$this->strType = "Saab";

Then the statement in question should now echo "Saab"

Though I think good practice here would be to not have the engine class contain a car object, just the car class should contain an engine object. And the properties would be better off as private. So you could have a car method like

public startEngine() {
    $success = $this->engine->start();
    if(success) {
        echo "Engine started successfully!";
    } else {
        echo "Engine is busted!";
    }
}

Where engine::start() returns a boolean.