如何将PHP回调作为非字符串传递，从而使其成为可重构的？

Question

Introduced in PHP 5.5, it is possible to use the MyClass::class syntax to reference a class instead of passing it as 'MyClass', which is not easily refactorable as it's just a string.

I would very much like to do the same thing with the function name, when passing a callback/callable to call_user_func() or usort().

In the example

usort($files, [FileFunctions::class, 'dircmp']);

only FileFunctions can easily be refactored.

How can I reference the dircmp function in a similar way?

Using

usort($a, FileFunctions::dircmp);

leads to a Undefined class constant 'dircmp' fatal error, as the parameter after the double colons is interpreted as a constant (of course).

Answer 1

<?php

class FileFunctions {
    static function dircmp($a, $b) {
        if ($a == $b) return 0;
        return ($a > $b) ? 1:-1;
    }
}

$files = [2,6,1,6,9,2,6,1,7,4];

usort($files, function($a, $b) {return FileFunctions::dircmp($a, $b);});
var_dump($files);

PHPStorm10 correctly refactored dircmp