In short, the Singleton Pattern is a design pattern used when we want only ONE instance of a class to be initialized. This is useful in CPU/Memory intensive classes, such as database handle abstractions.
The Singleton Pattern is a pretty fundamental pattern, worth learning about, if you aren’t already aware. It’s characterized by a private constructor, which can only be called by class member methods, and a public static accessor method, to return a reference to the object.
Here is a quick example of how it can be implemented in PHP (There are other ways, as well).
class Singleton {
private static $__instance;
protected $_value;
private function __construct() {
$this->_value = rand();
}
public static function getInstance() {
if(!isset(self::$__instance)) {
self::$__instance = new Singleton();
}
return self::$__instance;
}
public function display() {
echo $this->_value . "<br />";
}
}
Use it like this:
$foo = Singleton::getInstance(); $foo->display(); $bar = Singleton::getInstance(); $bar->display();
