php singleton

Singleton allows you to create an object that has only one instance, e.g. database class to avoid multiple connections:

class Database {

 private static $instance = false; 

 private function __construct() {
 $this->connect(); 
 }

 public static function getInstance() {

 if(self::$instance == false) {

 self::$instance = new Database();

 }

 return self::$instance; 

 }

 public function connect() {
 // create connection
 }

Then, instead of creating an object, you call a static method of Database class:

$db = Database::getInstance();

Notice the private constructor and $instance variable inside a class.