Question

How do I use an object (along with its methods and properties) when I’m inside an object?

Say I have useless classes like these:

class Fruit {
    private $name;          // Name of the fruit.
    private $health = 10;   // 0 is eaten, 10 is uneaten.
    private $object;        // This is a PHP object.

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

    public function set($varname,$value) {
        $this->$varname = $value;
    }
}

class Eater {
    private $name;

    public function eat($object) {
        $object->set('health',0);    // I know I can pass and modify objects like this.
        // The object is passed by reference in PHP5 (but not 4), right?
    }
}

And I use it as such:

<?php
    $pear = new Fruit("Pear");
    $apple = new Fruit("Apple");

    $paul = new Eater("Paul");
    $paul->eat($apple);
?>

But if I modify the Eater class like so:

class Eater {
    private $name;
    private $objectToEat;    // Let's say if I need the object to be over here instead of in a method.

    public function set($varname,$value) {
        $this->$varname = $value;
    }

    public function eat() {
        $this->objectToEat->set('health',0);    // This doesn't work!
    }
}

And set the main program like so:

<?php
    $pear = new Fruit("Pear");
    $apple = new Fruit("Apple");

    $paul = new Eater("Paul");
    $paul->set('objectToEat',$apple);
    $paul->eat();
?>

How can I access the object’s properties from inside a method? I know I use $this->objectToEat to tell PHP I’m talking about the class properity, but since that property is an object, how do I access the object’s methods?

I’ve tried $this->objectToEat->set('health',0) but that doesn’t work. I hope you guys understand what I’m trying to get at (sorry, I can’t figure out how to condense my question without compromising clarity)!

Answer 1

This answer modifies Renesis’ answer

In the class, the object to eat is a private variable hence you can’t go

$paul->objectToEat = $apple;

What you can do is to make a setter method inside Eaters

class Eaters {    
    private $name;    
    private $objectToEat;

    public function eat() {        
        $this->objectToEat->set('health',0); // Assumed "object" was just a typo    
    }

    public function setFood($object) {
        $this->objectToEat = $object;
    }
}

Therefore, you can call the setFood() method instead.

OR

Change eat() to

public function eat($object) {
    $this->object->set('health',0);
    return $object;
}

Saving the modified object back to the original variable.

OR

class Eaters {
    private $name;

    public function eat(&$object) { // this passes object by reference
        $object->set('health', 0);
    }
}

Although this code is not tested, that is how you can pass a variable by reference.

NOTE: You only need the & when defining the method not when you’re passing an argument. For more info about Passing by Reference go to this link