PHP closure

(PHP 5 >= 5.3.0, PHP 7)  Class used to represent anonymous functions.

function createGreeter($who) {
              return function() use ($who) {
                  echo "Hello $who";
              };
}

$greeter = createGreeter("World");
$greeter(); // Hello World

===============================

<?php

class A {

    public $base = 100;

}

class B {

    private $base = 1000;
}

$f = function () {
    return $this->base + 3;
};


$a = Closure::bind($f, new A);
print_r($a());

echo PHP_EOL;

$b = Closure::bind($f, new B , 'B');
print_r($b());

echo PHP_EOL;

上面的例子中，f这个匿名函数中莫名奇妙的有个f这个匿名函数中莫名奇妙的有个this,这个this关键词就是说明这个匿名函数是需要绑定在类中的。