(PHP 5 >= 5.4.0)
Closure::bindTo — Duplicates the closure with a new bound object and class scope
Create and return a new anonymous function with the same body and bound variables as this one, but possibly with a different bound object and a new class scope.
The “bound object” determines the value $this will
have in the function body and the “class scope” represents a class
which determines which private and protected members the anonymous
function will be able to access. Namely, the members that will be
visible are the same as if the anonymous function were a method of
the class given as value of the newscope
parameter.
Static closures cannot have any bound object (the value of the parameter
newthis should be NULL), but this function can
nevertheless be used to change their class scope.
This function will ensure that for a non-static closure, having a bound
instance will imply being scoped and vice-versa. To this end,
non-static closures that are given a scope but a NULL instance are made
static and non-static non-scoped closures that are given a non-null
instance are scoped to an unspecified class.
Note:
If you only want to duplicate the anonymous functions, you can use cloning instead.
newthis
The object to which the given anonymous function should be bound, or
NULL for the closure to be unbound.
newscope
The class scope to which associate the closure is to be associated, or 'static' to keep the current one. If an object is given, the type of the object will be used instead. This determines the visibility of protected and private methods of the bound object.
Returns the newly created Closure object
或者在失败时返回 FALSE
Example #1 Closure::bindTo() example
<?php
class A {
function __construct($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 $cl(), "\n";
?>
以上例程的输出类似于：
1 2
tatarynowicz at gmail dot com (2013-02-14 09:30:38)
You can do pretty Javascript-like things with objects using closure binding:
<?php
trait DynamicDefinition {
public function __call($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 (2012-03-09 13:35:02)
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 (2012-03-03 01:00:43)
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 (2011-12-18 16:23:48)
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
?>