How to apply factory pattern php

Question

I'm not sure how do factory pattern is applied.

If I take this code as example:

class Car
{
    protected $_engine;
    protected $_frame;
    protected $_wheels;

    public function __construct($engine,$frame,$wheels)
    {
        $this->_engine = $engine;
        $this->_frame = $frame;
        $this->_wheels = $wheels;
    }
}

class Engine
{
    protected $_hp;

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

class Frame
{
    protected $_type;
    protected $_length;

    public function __construct($type,$length)
    {
        $this->_type = $type;
        $this->_length = $length;
    }
}

class Wheels
{
    protected $_diameter;

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

class CarFactory
{
    // ???
}

How is the factory supposed to create all the parts of the car? Do I need a factory for every part? If so, how does the CarFactory know about them? The combination of IOC, DI and factory pattern confuse me where everything or anything should be initiated. I see the benefits of them all (I think).

How does Dependency Injection come into play here? Every part could have been its own object but for simplicity I left it out for now.

Hopefully my question is clear enough.

Thanks in advance!

Answer 1

You need to use factory if you have different types of cars.

class Car
{
    protected $type;

    public function drive()
    {
        echo 'Zoom-zoom!';
    }

    public static function factory($driven)
    {
        $instance = null;
        switch ($driven) {
            case 2:
                $instance = new Sedan;
                break;
            case 4:
                $instance = new Crossover;
                break;
            default:
                throw new Exception('Invalid driven type: ' . $driven);
        }

        return $instance;
    }
}

class Sedan extends Car
{
    // some things for sedan
}

class Crossover extends Car
{
    // some things for Crossover
}

$sedan = Car::factory(2);
$crossover = Car::factory(4);

$sedan->drive();
$crossover->drive();

Something like that.