在PHP中使用静态方法有什么好理由？

Question

有没有人有任何使用静态方法而不是动态的好例子？

Answer 1

辛格尔顿:

class SingletonClass {
    private static $instance;
    private function __construct() { }
    public function __clone() {
        trigger_error('Clone is not allowed.', E_USER_ERROR);
    }
    public static function init() {
        if (!isset(self::$instance)) {
            $c = __CLASS__;
            self::$instance = new $c;
        }
        return self::$instance;
    }
    // other public, dynamic methods for singleton
}

$singleton = SingletonClass::init();

跟踪实例数:

class CountMe {
    public static $instances = 0;
    public function __construct() {
        CountMe::$instances++;
    }
    public function __destruct() {
        CountMe::$instances--;
    }
}
$a = new CountMe();
$b = new CountMe();
echo CountMe::$instances; // outputs 2

Answer 2

当您不需要访问实例成员时。