PHP

Learn validation vs sanitization, filter_var, custom rules, and a reusable Validator class.

Learn PHP magic methods — __construct, __destruct, __get, __set, __toString, __invoke.

Learn static methods, static properties, utility classes, and the Singleton pattern.

Learn abstract classes vs interfaces with real-world examples and guidelines.

Understand PHP closures, use() capture, arrow functions, and uses with array functions.

Learn PHP type declarations, strict_types, union types, and nullable types.