Going deep with PHP

Going deep with PHP picks up where Going further with PHP left off. It assumes you have finished An introduction to PHP and Going further with PHP – project layout, Composer, prepared statements, routing, auth, and the two mini projects at the end of intermediate.

The intermediate tutorials taught you how to build a small app that does not fall apart on first contact with a real user. These tutorials are about the habits and patterns that keep projects maintainable when they grow: domain structure without cargo-cult DDD, middleware pipelines, security that goes beyond “escape output”, queues for slow work, caching that actually helps, PHPUnit habits that pay off, and WordPress PHP done properly (Codeskill runs on WordPress, so this is not optional trivia).

We also cover profiling and N+1 hunting, deployment basics (PHP-FPM, env config, migrations mindset), and two mini projects: a multi-user app with roles and a hardened public form with admin review. Plain PHP throughout – no Laravel, no Symfony. Patterns you can read, debug, and carry into any codebase.

You will need PHP 8.1 or newer, Composer, and a local stack you already use. PHPUnit appears in the testing lesson. Redis or a queue worker is optional for the queues tutorial – we show file-based fallbacks where that keeps the lesson runnable without extra services.

Work through the tutorials in order when you can. Where intermediate already explained something clearly, we link back rather than repeat it. If routing, sessions, or authorisation feel rusty, revisit those lessons first.