Closure::bindTo

(PHP 5 >= 5.4.0, PHP 7)

Closure::bindTo — 复制当前闭包对象，绑定指定的$this对象和类作用域。

说明

public Closure Closure::bindTo ( object $newthis [, mixed $newscope = 'static' ] )

创建并返回一个 匿名函数， 它与当前对象的函数体相同、绑定了同样变量，但可以绑定不同的对象，也可以绑定新的类作用域。

"绑定的对象"决定了函数体中的 $this 的取值，"类作用域"代表一个类型、决定在这个匿名函数中能够调用哪些 私有 和 保护 的方法。 也就是说，此时 $this 可以调用的方法，与 newscope 类的成员函数是相同的。

静态闭包不能有绑定的对象（ newthis 参数的值应该设为 NULL）不过仍然可以用 bubdTo 方法来改变它们的类作用域。

This function will ensure that for a non-static closure, having a bound instance will imply being scoped and vice-versa. To this end, non-static closures that are given a scope but a NULL instance are made static and non-static non-scoped closures that are given a non-null instance are scoped to an unspecified class.

Note:

如果你只是想要复制一个匿名函数，可以用 cloning 代替。

参数

newthis

绑定给匿名函数的一个对象，或者 NULL 来取消绑定。

newscope

关联到匿名函数的类作用域，或者 'static' 保持当前状态。如果是一个对象，则使用这个对象的类型为心得类作用域。 这会决定绑定的对象的 保护、私有成员 方法的可见性。

返回值

返回新创建的 Closure 对象 或者在失败时返回 FALSE

范例

Example #1 Closure::bindTo() 实例

<?php

class A {
    function __construct($val) {
        $this->val = $val;
    }
    function getClosure() {
        //returns closure bound to this object and scope
        return function() { return $this->val; };
    }
}

$ob1 = new A(1);
$ob2 = new A(2);

$cl = $ob1->getClosure();
echo $cl(), "\n";
$cl = $cl->bindTo($ob2);
echo $cl(), "\n";
?>

以上例程的输出类似于：

1
2

参见

User Contributed Notes

luc at s dot illi dot be 31-May-2016 01:44
Access private members of parent classes; playing with the scopes:
<?PHP
class Grandparents{ private $__status1 = 'married'; }
class Parents extends Grandparents{ private $__status2 = 'divorced'; }
class Me extends Parents{ private $__status3 = 'single'; }

$status1_3 = function()
{
    $this->__status1 = 'happy';
    $this->__status2 = 'happy';
    $this->__status3 = 'happy';
};

$status1_2 = function()
{
    $this->__status1 = 'happy';
    $this->__status2 = 'happy';
};

// test 1:
$c = $status1_3->bindTo($R = new Me, Parents::class);           
#$c();    // Fatal: Cannot access private property Me::$__status3

// test 2:
$d = $status1_2->bindTo($R = new Me, Parents::class);
$d();
var_dump($R);
/*
object(Me)#5 (4) {
  ["__status3":"Me":private]=>
  string(6) "single"
  ["__status2":"Parents":private]=>
  string(5) "happy"
  ["__status1":"Grandparents":private]=>
  string(7) "married"
  ["__status1"]=>
  string(5) "happy"
}
*/

// test 3:
$e = $status1_3->bindTo($R = new Me, Grandparents::class);   
#$e(); // Fatal: Cannot access private property Me::$__status3

// test 4:
$f = $status1_2->bindTo($R = new Me, Grandparents::class);   
$f();
var_dump($R);
/*
object(Me)#9 (4) {
  ["__status3":"Me":private]=>
  string(6) "single"
  ["__status2":"Parents":private]=>
  string(8) "divorced"
  ["__status1":"Grandparents":private]=>
  string(5) "happy"
  ["__status2"]=>
  string(5) "happy"
}
*/
?>

Clear the stack trace:
<?PHP
use Exception;
use ReflectionException;

$c = function()
{
    $this->trace = [];
};

$c = $c->bindTo($R = new ReflectionException, Exception::class);
$c();

try
{
    throw $R;
}
catch(ReflectionException $R)
{
    var_dump($R->getTrace());
}
/*
array(0) {
}
*/
?>
Nezar Fadle 19-Jan-2015 07:40
We can use the concept of bindTo to write a very small Template Engine:

#############
index.php
############

<?php

class Article{
    private $title = "This is an article";
}

class Post{
    private $title = "This is a post";
}

class Template{

    function render($context, $tpl){

        $closure = function($tpl){
            ob_start();
            include $tpl;
            return ob_end_flush();
        };

        $closure = $closure->bindTo($context, $context);
        $closure($tpl);

    }

}

$art = new Article();
$post = new Post();
$template = new Template();

$template->render($art, 'tpl.php');
$template->render($post, 'tpl.php');
?>

#############
tpl.php
############
<h1><?php echo $this->title;?></h1>
tatarynowicz at gmail dot com 14-Feb-2013 06:30
You can do pretty Javascript-like things with objects using closure binding:

<?php
trait DynamicDefinition {
   
    public function __call($name, $args) {
        if (is_callable($this->$name)) {
            return call_user_func($this->$name, $args);
        }
        else {
            throw new \RuntimeException("Method {$name} does not exist");
        }
    }
   
    public function __set($name, $value) {
        $this->$name = is_callable($value)?
            $value->bindTo($this, $this):
            $value;
    }
}

class Foo {
    use DynamicDefinition;
    private $privateValue = 'I am private';
}

$foo = new Foo;
$foo->bar = function() {
    return $this->privateValue;
};

// prints 'I am private'
print $foo->bar();

?>
safakozpinar at gmail dot com 09-Mar-2012 10:35
Private/protected members are accessible if you set the "newscope" argument (as the manual says).

<?php
$fn = function(){
    return ++$this->foo; // increase the value
};

class Bar{
    private $foo = 1; // initial value
}

$bar = new Bar();

$fn1 = $fn->bindTo($bar, 'Bar'); // specify class name
$fn2 = $fn->bindTo($bar,  $bar); // or object

echo $fn1(); // 2
echo $fn2(); // 3
anthony bishopric 03-Mar-2012 10:00
Closures can rebind their $this variable, but private/protected methods and functions of $this are not accessible to the closures.

<?php
$fn = function(){
    return $this->foo;
};

class Bar{
    private $foo = 3;
}

$bar = new Bar();

$fn = $fn->bindTo($bar);

echo $fn(); // Fatal error: Cannot access private property Bar::$foo
amica at php-resource dot de 19-Dec-2011 01:23
With rebindable $this at hand it's possible to do evil stuff:

<?php
    class A {
        private $a = 12;
        private function getA () {
            return $this->a;
        }
    }
    class B {
        private $b = 34;
        private function getB () {
            return $this->b;
        }
    }
    $a = new A();
    $b = new B();
    $c = function () {
        if (property_exists($this, "a") && method_exists($this, "getA")) {
            $this->a++;
            return $this->getA();
        }
        if (property_exists($this, "b") && method_exists($this, "getB")) {
            $this->b++;
            return $this->getB();
        }
    };
    $ca = $c->bindTo($a, $a);
    $cb = $c->bindTo($b, $b);
    echo $ca(), "\n"; // => 13
    echo $cb(), "\n"; // => 35
?>