Example of Singleton Pattern

gistfile1.php

class classB {
    private static $instance;
    private $count = 0;
    private function __construct() {}
    static function functionB() {
        if (!isset(self::$instance)) {
            $className = __CLASS__;
            self::$instance = new $className;
        }
        return self::$instance;
    }
    public function increment() {
        return $this->count++;
    }
}

$b = classB::functionB();
echo $b->increment(); // 0
echo $b->increment(); // 1

$b = classB::functionB();
echo $b->increment(); // 2
echo $b->increment(); // 3