Question

I am currently a beginner in PHP OOP programming and was wondering if someone could provide an example of how using static properties and methods are useful in real web applications.

Answer 1

Although statics can have problems as pointed out in the comments, they do have a few uses.

One which I’ve found quite useful is “named constructors”.

Typically a class would have a single constructor. But what if the class could be initialized in several different ways?

For example, perhaps your application supports creating users with an email address, or from a Facebook User ID…

class User {
    public function __construct($emailOrFbUserId) { } 
}

As you can see above, it could be a bit confusing to what the parameter in the constructor was when you use the class.

Instead, by writing it like this…

class User {
    private function __construct() { }

    public static function fromEmailAddress($email) {
        $user = new User();

        //assuming there's a private field called email
        $user->email = $email;
        return $user
    }

    public static function fromFacebookUserId($id) {
        ...
    }
}

//usage example
$user = User::fromEmailAddress('[e-mail]');

…and it suddenly makes much more sense.