MC-34097 Update supported PHP version

[dobooth]

Purpose of this pull request

This pull request (PR) updates v2.4 to use the latest supported PHP version.

whatsnew
Updated the supported versions of PHP to 7.3 and 7.4.

[keharper]

I see several v2.3 files in this PR. Is that intentional?

[jeff-matthews]

I was unable to leave comments in the previously symlinked files due to the notorious "Line must be part of the diff" known issue.

• src/guides/v2.4/install-gde/prereq/php-settings.md
  • line 14: lliquid script should point to 2.4 composer lock file.

[dobooth]

running tests

[ghost]

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[hunt0r]

I feel silly posting this here, so please delete if it's inappropriate.
@jeff-matthews your post above references 'the notorious "Line must be part of the diff" known issue'. I have encountered that issue, but unable to find it with Google/Github support searching. My Google-searching led me here 😆 Would you mind sharing a link about it?

[jeff-matthews]

Hi @hunt0r! I wish I could share a link, but I was actually referring to this being "notorious" for those of us working on this particular project. I think everyone on the devdocs-admins team has encountered it at some point.

All we really know is that it has something to do with files that were previously symlinked in our project. For example, after deleting the symlink for src/guides/v2.4/install-gde/prereq/php-settings.md, creating a new/"real" file, and adding/pushing, the GitHub interface throws that error if you try to leave inline comments during review.

We haven't been able to track down any official root cause. So if you find something, please come back and let us know!

[hunt0r]

That is exactly my case. Unfortunately, it is on a private repo with proprietary code so I can't provide an example.
We had one "file" which was merely a symlink to another.
I deleted the symlink and then copied another file into the same place. Git seemed to handle this fine.
I pushed to github, and then went to write a comment on one line of the file. But got that error, and could not post my comment.

Thanks for the response. Since I can't provide an example, I am hesitant to open a Github support ticket. But if you are willing to open one, please let me know if I can help in some way.