One of the main advantages of using PHP is its awesome, large and diverse community behind it. The community consists of PHP libraries, frameworks, CMSes and other PHP applications and also great, open minded people that are connected with each other one way or another.
PHP User Group (PUG) is virtual or real in-place community consisting of local people participating and organizing PHP conferences and meetings. You can find your local user group at official PHP user groups list which is based on the PHP.ug. In case there is no local PHP User Group near you, find some friends interested in PHP and start your own local user group.
Many meetup and conference organizers use also Meetup for organizing and sharing PHP meetings.
Many of the popular PHP Content Management Systems (CMSs) have an active and supportive community, both online and in the real world.
Some of the popular frameworks and their online forums:
Additional interesting and amazing resources about PHP community: