一个类中的闭包数组

Question

It appears you can't have an array of callable methods defined within the scope of a class. Why not?

Why is this valid PHP (see http://3v4l.org/1JeQr)

$methods = array(
    1 => function($subject, $value){
        return ($subject == $value);
    }
);

var_dump($methods[1]('a', 'a'));

But not this (see http://3v4l.org/FL449)

class Foo {
    public static $methods = array(
        1 => function($subject, $value){
            return ($subject == $value);
        }
    );
}

var_dump(Foo::$methods[1]('a', 'a'));

Answer 1

A very quick answer since I am working from mobile phone (can eventually edit later.

Defining a closure actually performs an instantiation of an object of type Closure. PHP only supports native internal types as default values for your classes, which means that constructing a closure obviously won't work.