ENH add nullable return types

[lekoala]

Description

More phpdoc updates

Don't merge yet, more updates are coming related to date fields

Issues

• Improve phpdoc types #11173

Pull request checklist

• The target branch is correct
  • See picking the right version
• All commits are relevant to the purpose of the PR (e.g. no debug statements, unrelated refactoring, or arbitrary linting)
  • Small amounts of additional linting are usually okay, but if it makes it hard to concentrate on the relevant changes, ask for the unrelated changes to be reverted, and submitted as a separate PR.
• The commit messages follow our commit message guidelines
• The PR follows our contribution guidelines
• Code changes follow our coding conventions
• This change is covered with tests (or tests aren't necessary for this change)
• Any relevant User Help/Developer documentation is updated; for impactful changes, information is added to the changelog for the intended release
• CI is green

[GuySartorelli]

Setting to draft since it says not to merge it yet

[GuySartorelli]

As a general rule, please try to avoid creating a PR which isn't ready to merge yet. We're a lot more likely to notice a new PR (and start looking at it) than we are to notice updates to an existing PR.

[lekoala]

@GuySartorelli didn't get the time to make the other changes i was planning to so this can be merged as is, i will reopen a new one when i find the time to make more improvements