- PHP 7.4 and 8.0 have been EOL https://www.php.net/supported-versions.php
- See go/drop-php-8.0 for more details
Most of the changes came from `generate_projects.sh` after updating the `tools/buildgen/plugins/expand_version.py` file. The change to `tools/internal_ci/helper_scripts/prepare_build_macos_rc` is manual.
Closes#35964
COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35964 from stanley-cheung:php-update-to-8_1 0c24c4eac21acae9208473363b1d3f737976ccd3
PiperOrigin-RevId: 609495798