Routing
Map GET and POST requests directly to controller actions.
PHP + MySQL + MVC
Small enough to understand. Useful enough to build on.
Sevown Stack is a dependency-light starter for database-backed PHP applications.
PDO
Use prepared statements without an ORM or hidden query layer.
Views
Render plain PHP templates inside a simple layout.
Security basics
Sessions, CSRF tokens, password verification, and safe output escaping.