Fix the functions/methods signatures

[letrunghieu]

After version v3.0.0-alpha.3 was release, there is still a bug on displaying scalar return type. Not nullable types (int, bool, ...) is missing from the output HTML while the nullable types (?int, ?bool, ...) is displayed incorrectly as int, bool, ...

For example, this is a test input file:

<?php

class Foo {
	public function getInt(): int {return 1;}
	public function getOptionalInt(): ?int {return null;}
}

With the v3.0.0-alpha.3 release, the output document is:

With this PR, the output document is

This PR also fixes #2020

[jaapio]

Thanks for this PR. Before I can merge this I need to update the other templates and add a note for other template developers that the need to update their templates.

[jaapio]

I checked the code that should provided the types. But I think we discovered a bc break here.
Thanks for pointing us on this break. We fixed it in the code so templates don't need changes right now.

The current version in develop should not have this issue any more.