➡ Data Formats & Types (xml, json, soap) ➡ web features (sessions, cookies, auth) ➡ OOP (interfaces, exceptions, LSB, SPL) ➡ Security (sql injection, filtering, ssl) ➡ IO (files, streams, contexts) ➡ Strings (match, regex) ➡ Databases (SQL, joins, pdo) ➡ Arrays (multi-dimension, spl, array functions) 59