Request for Comments: Invokable

• Version: 1.0
• Date: 2008-08-02
• Author: Etienne Kneuss colder@php.net
• Status: Under Discussion

Closures were implemented in PHP_5_3. For them, an __invoke() magic method was implemented, but not only for closures, every classes can define their own __invoke() and then use $obj();

Currently, there is no sane way to detect whether an object can be invoked or not. What this RFC proposes is an interface that covers __invoke():

interface Invokable {
   public function __invoke($args);
}
 
class Closure implements Invokable {
/* ... */
}
 
class MyClass implements Invokable { 
/* ... */
}

And make $obj(); possible only if the interface is implemented, and not only the method. We have other examples of magic features that are covered by interfaces, like ArrayAccess or Iterator/Traversable.