This may be deeply stupid, but I'm new to IRC, and I'm getting a message on Freenode saying "Cannot join #php (Channel is invite only)". Am I missing something? Or is it possible to just watch the discussion without participating and that doesn't require an invite?
Freenode uses ##<channel> to refer to "non-primary" channels. Regardless of what that means (I don't really know), the channel you're looking for is ##php.