Write the 14 PHP intermediate modules

Part of the content gap. The manifest declares 14 PHP intermediate modules (php-i-01..php-i-14); none are written.

Files go in content/php/intermediate/<index>.md, one per module, matching the manifest order. See the README for the markdown conventions — in particular, every ## heading becomes a separately tracked section in the player, so section splits are structural.

Already decided for this level

Three things were deliberately deferred from beginner to intermediate on 2026-06-11, because each spans two layers at once and only makes sense once both are familiar:

• Initial State (IInitialState / loadState()) → php-i-07 (REST API Design), framed as "how to avoid an API roundtrip on page load". Tracked separately.
• @nextcloud/dialogs (showSuccess/showError) → not yet placed in a module. Tracked separately.
• Admin settings (IAppConfig, distinct from per-user IConfig) → php-i-11. Tracked separately.

Source material

course/files/tutorials/ holds the older tutorial library, useful as a cross-check rather than as content. Everything in it uses docker-compose (v1, EOL) and needs docker compose.

Done when

All 14 modules have content files and appear correctly in the player.

Start with the manifest and README to confirm the 14-module order and markdown conventions, then review the older material in course/files/tutorials/ as a cross-check, updating docker-compose usage to docker compose. Create php-i-01 through php-i-14 under content/php/intermediate/, preserving structural ## sections and the explicitly assigned topics. Done means all 14 files exist and appear correctly in the player.