deprecate-php
Read DEPRECATING.md and follow it exactly. That file is the single source of truth for deprecating PHP in this repo and is shared across tools.
@../../../DEPRECATING.md
The guide itself references:
AGENTS.md: agent behaviour rules, including the pointer to the guide.config/dependency-injection/deprecated-classes.php: the DI container's deprecated-classes list.
If any step in the guide appears to conflict with AGENTS.md or .github/CONTRIBUTING.md, the rule files win. Edit them, then update the guide.