Since LinkedIn opened up its Groups system, there has been a huge growth in the number of groups related to PHP.  Some with charters, some without; some with a specific community background and others with a specific regional focus.  I am posting this to bring attention to some of them.

In order of popularity (member count) some general groups (non-regional) are:

• LinkedPHPers
• Php developers
• PHP
• PHP language
• PHP Technology Specialists
• PEAR
• PHP Developer Network
• PHP User Group

Some of these are useful if you are looking for a job (the recruiters tend to play nice and stay on-topic), others ban job posts and stick to discussions.
There are literally hundreds of groups related to PHP in some shape or fashion - pure PHP, LAMP, PHP&Mysql, Frameworks, and many regional *PUG type groups.