Namespaces that prepend the current namespace - php

Question

I have a class wrapper, class car, that lives in the namespace of Automobile. Then I have class tire that lives in the namespace of Automobile\Wheels. In the tire class, I want to access a static variable from the car class, but the only way to do that is to reference the complete namespace\class.
<?php
namespace Automobile;
class Car {
public static $Axle;
public function __construct() {
static::$Axle = new Axle();
}
}
<?php
namespace Automobile\Wheels;
class Tire {
public $size;
public function __construct($size = 16) {
$this->size = $size;
\Automobile\Car::$Axle->add_wheel($this);
}
}
My questions are: is it an okay practice to reference classes like this? Are there any ways to reference the class without including the complete and absolute namespace for the class?

Answer 1

There's really no good or bad way to do it, although people might be quite opinionated about it (the same with using spaces or tabs for indents, but let's not go down that road ;) ). As long as they're properly referenced it's okay to use fully qualified class names.
You might want to use the use keywords to 'import' external classes, which improves the readability in my opinion:
<?php
namespace Automobile\Wheels;
use Automobile\Car;
class Tire {
public $size;
public function __construct($size = 16) {
$this->size = $size;
Car::$Axle->add_wheel($this);
}
}
You might want to reference the PHP documentation, as it is quite concise about the subject and gives good insight in how to use namespaces.

Answer 2

As others have pointed out, use use for the full namespaced class (e.g., use Automobile\Car;). From there, you can use the shortened class reference (e.g., Car) throughout the rest of the file.
As an aside, it's best practice to avoid statically invoking properties and method if at all possible. It's generally considered best practice to inject your dependencies as it decouples your code and allows for swapping out of pieces of your application using interfaces.
I would do something like this:
<?php
namespace Automobile;
class Car {
/** #var Axle */
public $axle;
public function __construct(Axle $axle) {
$this->axle = $axle;
}
}
<?php
namespace Automobile\Wheels;
use Automobile\Car;
class Tire {
public $size;
public function __construct(Car $car, $size = 16) {
$this->size = $size;
$car->axle->add_wheel($this);
}
}