Put research on a PHP 8.x floor on the roadmap

[dknauss]

Summary

This puts the PHP 8.x floor question on the roadmap as research, with no decision made.

• New pending todo, .planning/todos/pending/2026-10-14-research-php-8x-floor.md. It holds the first findings, checked against main:
  • Performance: no gain. How fast PHP runs depends on the host, not on the declared floor.
  • Leaner code: a few lines.
    • PHPCompatibilityWP finds zero 7.4 violations.
    • One helper, is_list_array(), would become array_is_list().
    • There's no switch code for match to replace.
  • Maintainability: modest, mostly from native types. Plus two fewer runtime-matrix cells.
  • Audience: WordPress core still supports 7.4. About 62% of WordPress.org-reporting sites run PHP 8.2 or older.
  • Research still to do: current version shares, core's own minimum plans, what comparable plugins require, a typed-code estimate, and how to warn sites.
  • Recommendation so far: keep 7.4. Revisit when core moves to 8.x or 7.4 falls below about 5% of installs. If the floor is raised, go straight to 8.1.
• The owner's note, recorded in three places (the todo, the roadmap entry, and the memo's Phase D): Phase D (Psalm tightening) gets most of the maintainability benefit of a PHP 8.x floor with nobody left behind.
• .prettierignore now ignores .claude/. Claude Code agent worktrees are whole checkouts, and they made format:check flag 110 files locally.

Validation

• Docs and planning only.
• npm run format:check: passes, including with agent worktrees present.

Checklist

• No code changed

🤖 Generated with Claude Code

https://claude.ai/code/session_01KbVuMPN7YTcV27vwsG3LZ2

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.28%. Comparing base (7a13b48) to head (c6ba1bb).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #154   +/-   ##
=========================================
  Coverage     88.28%   88.28%           
  Complexity       22       22           
=========================================
  Files            61       61           
  Lines          7290     7290           
  Branches        690      690           
=========================================
  Hits           6436     6436           
  Misses          291      291           
  Partials        563      563           

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