PHP Generator: address PSR-12 formatting violations

[gcatanese]

This pull request refactors the ObjectSerializer Mustache template to avoid generating code that is not aligned to PSR-12 guidelines.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
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@jebentier (2017/07), @dkarlovi (2017/07), @mandrean (2017/08), @jfastnacht (2017/09), @ybelenko (2018/07), @renepardon (2018/12)

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Summary by cubic

Align PHP generator output with PSR-12 by cleaning up formatting in the ObjectSerializer template. This keeps generated clients lint-clean without changing behavior.

• Refactors
  • Standardize casting, foreach spacing, and add braces to single-line if statements.
  • Replace hash comments with slashes and fix docblock indentation.
  • Tidy query helpers: correct deepObject flattening prop assignment and guard returns with braces.
  • Normalize \DateTime checks and spacing in query value handling.
  • Regenerate PHP samples to reflect the template updates.

^{Written for commit 8c3059e. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files