php 中的魔术方法-----“事件方法”

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 php 中的这个对象 ，有时间研究一下：

 

PHP中会有一些魔术方法：PHP 将所有以 __（两个下划线）开头的类方法保留为魔术方法。所以在定义类方法时，除了上述魔术方法，建议不要以 __ 为前缀。

魔术方法有：​​__construct()​​， ​​__destruct()​​， ​​__call()​​， ​​__callStatic()​​， ​​__get()​​， ​​__set()​​， ​​__isset()​​， ​​__unset()​​， ​​__sleep()​​，​​__wakeup()​​， ​​__toString()​​， ​​__invoke()​​， ​​__set_state()​​， ​​__clone()​​ 和 ​​__debugInfo()​​ 等方法在 PHP 中被称为"魔术方法"（Magic methods）。在命名自己的类方法时不能使用这些方法名，除非是想使用其魔术功能。

 

Typehint

PHP has a variety of magic methods; methods named with two underscores at the start, which get called automatically when a particular event happens.（所以我标题中也叫事件方法，指特定的时间触发时，会自动调用，自动执行的方法。） In PHP 5.3, a new magic method was added: ​​__invoke()​​.

__invoke()

The ​​__invoke()​​ method gets called when the object is called as a function. When you declare it, you say which arguments it should expect. Here's a trivially simple example:

class Butterfly {
  public function __invoke() {
    echo "flutter";
  }
}

We can instantiate a Butterfly object, and then just use it like a function:

$bob = new Butterfly();
$bob(); // flutter

If you try to do the same thing on an object without an ​​__invoke()​​ method, you'll see this error:

PHP Fatal error:  Function name must be a string in filename.php on line X

We can check if the object knows how to be called by using the ​​is_callable()​​ function.

Callable Typehint

In PHP 5.4 (the newest version, and it has lots of shiny features), we have the ​​Callable​​ typehint. This allows us to check whether a thing is callable, either because it's a closure, an invokable object, or some other valid callback. Another trivial example to continue the butterflies and kittens theme:

 

也就是说， php 中 callable类型一共有3种： 

 

function sparkles(Callable $func) {
  $func();
  return "fairy dust";
}

class Butterfly {
  public function __invoke() {
    echo "flutter";
  }
}

$bob = new Butterfly();
echo sparkles($bob); // flutterfairy dust

So there it is, one invokable object being passed into a function and successfully passing a ​​Callable​​ typehint. I realise I also promised kittens, so here's a cute silver tabby I met the other day: