Hi Almgren,
I'm fairly new to PHP as well, but I've found that the approach that works for me involves some jumping around between ongoing, systematic reading of books and quick searches in the online documentatation at php.net and--in this case---the Joomla/Mambo code--to fill in the syntax gaps native to its API.
The first book I bought was O'Reilly's "Programming PHP", because it was thorough and practical, and the reading was scaffolded in a way that could probably accomodate any level of experience:
www.oreilly.com/catalog/progphp/
It got through to me because I was coming from two different directions: a design (artsy stuff) and a design (database) background. To me, the content seemed to speak to both perspectives. That was nice.