⬆️ Bump minimum PHP to 8.3

[retlehs]

Bump minimum PHP version to 8.3

This PR raises Bedrock's minimum PHP requirement from 8.1 to 8.3.

Why 8.3 (not 8.2)?

PHP 8.1 reached end of life on December 31, 2025.
PHP 8.2 reaches EOL in December 2026, which would force another bump soon.
PHP 8.3 receives security support through December 2027, giving this change a longer useful window.

Ecosystem alignment

The Roots ecosystem is converging on 8.3:

• Radicle already requires PHP 8.4 minimum
• Trellis defaults to PHP 8.3
• Laravel 13 requires php: ^8.3, which aligns with Acorn's direction

Setting 8.3 here keeps Bedrock consistent with the tools most users are running alongside it.

Adoption

Per WordPress.org stats, PHP 8.3 is at ~19% of WordPress installs. Bedrock's audience (developers managing their own infrastructure via Trellis, containers, or local dev tools) is well-positioned to be on 8.3 already.

If your project requires an earlier PHP version, adjusting the php constraint in composer.json is a one-line change.

Sources:

• Trellis default php_version: "8.3": https://github.com/roots/trellis/blob/master/group_vars/all/main.yml
• Laravel 13 PHP requirement (^8.3): https://github.com/laravel/framework/blob/13.x/composer.json
• WordPress requirements (recommended 8.3+): https://wordpress.org/about/requirements/
• Docs update for Bedrock PHP 8.3: Update Bedrock minimum PHP requirement to 8.3 docs#569