What should every PHP programmer know? [closed]

Answer 1

All good answers, but there is something important missing: If you want to seriously get into PHP, then you should be aware that there are a lot of PHP programmers out there who are lazy, inept, ignorant, misguided and unfortunately get their code released to the public. The history of PHP means that it supports some questionable features (not just things like register_globals but also smaller things like automatic initialization) and people still use them. You don't want to.

Answer 2

You need to learn the following (I would suggest in this order):

1. Basic Object-Oriented Principles (such as inheritance, polymorphism, and encapsulation)
2. The PHP language itself. Specifically, PHP 5.
3. Database Design Principles such as tables, keys, relationships, normalization, etc.
4. SQL - Structured (or Standard never can remember which) Query Language. Specifically learn the basics of select, insert, update, and delete queries.
5. Good design principles and coding practices (you can find posts here on StackOverflow for one) such as dividing presentation and business logic.
6. A Framework, Any Framework - this will help you become introduced to more advanced concepts of object-oriented design patterns and allow you to follow tutorials that will encourage good design and coding practices.
7. Object-Oriented Design Patterns like MVC, Database Abstraction Models and the like
8. Advanced SQL and other database stuff like triggers, stored procedures, and other functions.