What is the output of the following code? class Number { private $v; private static $sv = 10; public function __construct($v) { $this->v = $v; } public function mul() { return static function ($x) { return isset($this) ? $this->v*$x : self::$sv*$x; }; } } $one = new Number(1); $two = new Number(2); $double = $two->mul(); $x = Closure::bind($double, null, 'Number'); echo $x(5);