[PhpUnitBridge] Simplify the code when only installing

[johnstevenson]

Q	A
Branch?	4.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets	-->
License	MIT
Doc PR

This PR makes the code clearer when only installing and removes extraneous work if the phpunit symlink/junction just needs updating. It additionally fixes a couple of inconsistencies.

This is the first of a few of other minor fixes I would like to propose, which have been split up to be merge-upable friendly.

[nicolas-grekas]

Hi, thanks for the PR. From the description, this doesn't fix a bug but is a code refactorization, right? This should target 6.1 if confirmed.
Otherwise, please describe the bug.

[GromNaN]

If we are to refactor this code (and target 6.1), we could use a class (with a basic require_once). It would be testable and certainly more readable.

[johnstevenson]

@nicolas-grekas Yeah, I was probably stretching the bug bit: it was more about improving performance, though there is an inconsistency in $getEnvVar not returning the default when the env is an emtpy string (only fixed for the the case that caused an issue) - which would have been my second improvement.

My overall plan was to simply get the code into a more readable state for the supported versions so that:

1. it is easier for folks to make fixes in the future
2. it is easier to refactor it into a class (in the future).

I'll do whatever you suggest.

[nicolas-grekas]

Note that refactoring for the sake of it might not be worth it. We have a track record of refactorings that break things so we're quite prudent now :)

[johnstevenson]

I've put all the changes I wish to make as a separate PR: #44668

[fancyweb]

@johnstevenson Can we close this one in favor of #44668? 🤔

[johnstevenson]

Can we close this one in favor of #44668?

I didn't get a specific answer here, so I created that PR to show the full extent of the changes I wished to make.

So I guess someone needs to decide if it would be cleaner to incorporate these fixes/changes on 4.4, or whether they should only be made on 6.1.

[nicolas-grekas]

We won't merge a refactor on 4.4, so closing here.