I don't think it is correct to generate code which will put an argument with a default value before an argument without a default value.

In the example the generated code produces a function like that:

function bar(int $a = null, string $b, bool $c, callable $d = null) : float

This means the first argument is optional, but the second and third aren't.

I realise = null i

I'm wondering, does it really make sense to add documentation to our functions, if they're barely a wrapper to the original ones?

Unless there are gotchas, I would just leave:

/**
 * @link http://php.net/manual/en/function.xxx.php
 */

If we change something apart from the name of the function itself, we could just add a note:

/**
 * @link http://php.net/manual/en/