got to agree. php.net is always my first stop if I can't remember a functions parameters. You can also download the php.net documentation in chm format for your desktop.
Another coupls of good books are:
core php by atkinson/suraski. Should be on any pro php developers shelves.
php - objects, patterns & practice by Zandstra. Advanced OOP stuff showing the real future of php architected web programming.
S