手册中　Closure::bind — 复制一个闭包，绑定指定的$this对象和类作用域。

　　具体参数可以看手册，这里记录下这个方法的实际用处．

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     methods[$methodName] = Closure::bind($methodCallable, $this, get_called_class());14 15     }16 17     public function __call($methodName, array $args)18     {19         if (isset($this->methods[$methodName])){20             return call_user_func_array($this->methods[$methodName],$args);21         }22 23         throw new RuntimeException('There is no method with the given name to call');24 25     }26 27 }28 29 class HackThursday30 {31     use MetaTrait;32 33     private $dayOfWeek = 'Thursday';34 }35 36 37 $test = new HackThursday();38 $test->addMethod('when',function(){39     return $this->dayOfWeek;40 });41 42 echo $test->when(); //Thursday

　　其实这个方法就是以前说过的  的静态版本, 和这篇一起看加深理解．