1. API Authentication
2. Array functions name (PHP).
3. Differences between '==' and '===' in PHP
4. Database normalization
5. Difference between session and cookie
6. Break and continue
7. Web Application Security.
8. Caching
9. include, require, require_once
10. Software Lifecycle
11. Inheritance in OOP
12. Agile Methodology
13. Overriding and Overloading