config/php.md: docs to help users with metapackage transition

Author: TinfoilSubmarine

src/SUMMARY.md

@@ -69,6 +69,7 @@
       - [libvirt](./config/containers-and-vms/libvirt.md)
       - [LXC](./config/containers-and-vms/lxc.md)
    - [OpenPGP](./config/openpgp.md)
+   - [PHP](./config/php.md)
 - [XBPS Package Manager](./xbps/index.md)
    - [Advanced Usage](./xbps/advanced-usage.md)
    - [Repositories](./xbps/repositories/index.md)

src/config/php.md

@@ -0,0 +1,35 @@
+# PHP
+
+There are two ways to install PHP packages with XBPS:
+
+1. Using the versioned packages (recommended).
+2. Using the meta-packages.
+
+## Versioned PHP Packages
+
+It is generally recommended to use versioned PHP packages (e.g. `php8.1`,
+`php8.1-apcu`, etc.) for most use cases as this ensures a consistent environment
+on updates with minimal or no intervention required.
+
+## PHP Meta-packages
+
+In Void, the `php` package is a meta-package that points to the latest upstream
+PHP version. This convention is followed by all packages prefixed with `php-`,
+such as `php-fpm`, as well as `xdebug` and `composer`. See [the `php`
+template](https://github.com/void-linux/void-packages/blob/master/srcpkgs/php/template)
+for a complete list. It is recommended to only use these meta-packages for
+development purposes.
+
+When using a PHP meta-package, be warned that updating may require manual
+intervention if a new major PHP version has been added to the repository. As a
+part of the version change, the configuration location will change to reflect
+the new version. For example, upgrading from 8.0 to 8.1 would result in the
+configuration path changing from `/etc/php8.0` to `/etc/php8.1`. Any
+customizations that have been made need to be manually applied to the new
+configuration directory.
+
+`php-fpm` updates require special care since they include a runit service. In
+this case, ensure that the new runit service is started and that applications
+using the previous version of `php-fpm` can access the new `php-fpm` instance.
+In particular, make sure any applications accessing the FPM instance have the
+correct TCP/unix socket address.