When it comes to online, PHP-specific content, there's quite a lot on offer. Outside of the main PHP site, Zend has a very good set of PHP tutorials, and they also print various other popular editorials about the state of PHP. PHP Builder publishes a number of high-quality PHP tutorials each year, and also have very active forums full of people ready to help. One other popular PHP web site is DevShed - isn't as good as PHP Builder by any means, but will provide another possible resource if you have questions.
Several application vendors also try to boost their marketing efforts by offering PHP content. Oracle is perhaps the most prevalent - they had several top PHP hackers write the Hitchhiker's Guide to PHP , which is available online for free. Similarly, IBM developerWorks has published a number of PHP tutorials, some of which are actually good.