Closure::bind

(PHP 5 >= 5.4.0, PHP 7, PHP 8)

Closure::bind — Duplicates a closure with a specific bound object and class scope

Description

public static Closure::bind(Closure $closure, ?object $newThis, object|string|null $newScope = "static"): ?Closure

This method is a static version of Closure::bindTo(). See the documentation of that method for more information.

Parameters

closure: The anonymous functions to bind.
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 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. It is not allowed to pass (an object of) an internal class as this parameter.

Return Values

Returns a new Closure object, or null on failure.

Examples

Example #1 Closure::bind() example

<?php
class A {
    private static $sfoo = 1;
    private $ifoo = 2;
}
$cl1 = static function() {
    return A::$sfoo;
};
$cl2 = function() {
    return $this->ifoo;
};

$bcl1 = Closure::bind($cl1, null, 'A');
$bcl2 = Closure::bind($cl2, new A(), 'A');
echo $bcl1(), "\n";
echo $bcl2(), "\n";
?>

The above example will output something similar to:

1
2

User Contributed Notes 2 notes

down

Vincius Krolow ¶

12 years ago


With this class and method, it's possible to do nice things, like add methods on the fly to an object.

MetaTrait.php
<?php
trait MetaTrait
{
    
    private $methods = array();
 
    public function addMethod($methodName, $methodCallable)
    {
        if (!is_callable($methodCallable)) {
            throw new InvalidArgumentException('Second param must be callable');
        }
        $this->methods[$methodName] = Closure::bind($methodCallable, $this, get_class());
    }
 
    public function __call($methodName, array $args)
    {
        if (isset($this->methods[$methodName])) {
            return call_user_func_array($this->methods[$methodName], $args);
        }
 
        throw RunTimeException('There is no method with the given name to call');
    }
 
}
?>

test.php
<?php
require 'MetaTrait.php';
 
class HackThursday {
    use MetaTrait;
 
    private $dayOfWeek = 'Thursday';
 
}
 
$test = new HackThursday();
$test->addMethod('when', function () {
    return $this->dayOfWeek;
});
 
echo $test->when();

?>

down

potherca at hotmail dot com ¶

10 years ago


If you need to validate whether or not a closure can be bound to a PHP object, you will have to resort to using reflection.

<?php

/**
 * @param \Closure $callable
 *
 * @return bool
 */
function isBindable(\Closure $callable)
{
    $bindable = false;

    $reflectionFunction = new \ReflectionFunction($callable);
    if (
        $reflectionFunction->getClosureScopeClass() === null
        || $reflectionFunction->getClosureThis() !== null
    ) {
        $bindable = true;
    }

    return $bindable;
}
?>

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