I'm needing to help my friend with his big phpBB board, but I want first to learn the basics of PHP very very fast. I just want to learn the basics to go and improving with some more time. In the books you need to take time to read, but I need to learn more faster, there is any suggestion?
phpbb is an open source project. also, mainly the setup is done via web gui
If you're interested in learning the basics, you should probably stay away from PHPBB's source code. Even if you gained a solid understanding of the basics, I would still encourage you to not touch PHPBB as a first project.
Be honest, tell your friend that you are in no position to help him - yet. I learned the basics many moons ago from w3schools and the online documentation. Unfortunately for me, a site like stackoverflow didn't exist back then, so I couldn't use it, but that isn't so with you. Use this site, and use it frequently!
Go read the language sections of the manual http://www.php.net/manual/en/index.php
Correct me if I'm wrong, but I suppose you have at least some programming background. I'll not tell you how to learn, instead I'll tell you WHAT to learn.
If you are used to any other language that has C-style syntax (Java, C#...), you already know the syntax. Conditional statements, loops,assignments and other basic operations have the same structure, and you'll have to learn just some language-specific rules (for example, variables have the $
prefix and doesn't need to be declared before use).
The next step is input and output. Understand how HTTP requests work and how the requests trigger your PHP scripts. Learn how to use output functions (echo, print, etc) to generate pages and how to deal with default input arrays ($_GET, $_POST, $_COOKIE, $_SESSION...).
Later I would focus in database connectivity, starting with MySQL. Why? Because MySQL is very popular, and used by many of open source projects, including phpBB AFAIK. Check the web for some begginner tutorials, but also look at php.net official documentation, they're pretty good.
Learning OO in PHP is nice, but won't help you too much in this case. Most of these open source projects support older versions of PHP, then features added (or improved) by recent versions of the language are avoided. I'm not saying that you don't have to learn it, just telling you to postpone it.