[PHP] 'ConstructMe' class - confused!

Well, I was recently watching my friend coding a small guestbook for his website, and he was trying out new areas of PHP and wrote a 'constructme' class, here is the coding:

Code:

---

                public static function constructMe() {
                        if(!self::$_instance instanceof self) {
                                self::$_instance = new self();
                        }
                        return self::$_instance;
                }

---

But, what the hell does it do? How does it work, and if I were to use it, how would I? D:

Thanks!

wtf?

is he trying to make a singleton?

if so:

PHP Code:

---

    public static function singleton() {
        if(!isset(self::$instance)) {
            $class = __CLASS__;
            self::$instance = new $class;
        }
        return self::$instance;
    } 


---

I've got no idea, all I know is, it worked for what he wanted to do..

But what does it actually do? Is it used to instantiate classes? If so, how do I go about using it throughout my work?

Basically, it's to make it so you can only instantiate a given class one time during the lifetime of the script- the whole script.

More detail and some direction here:
How to use the Singleton design pattern - TalkPHP

More design patterns here,
http://www.fluffycat.com/PHP-Design-Patterns/

Ahhh, okay, thank you :)