Simple Community Forum in PHP

I need one simple Community Forum that will be build by using PHP Language. by the way i don't want it to be build by using CMS. what i want is just a simple forum completely done by using PHP language.

Requirements are :

2 User: admin and user.
Have avatar for user profiles.
Forum Topics
Forum Post
Post Reply
Message between user.

thats all i need in this simple forum.

please take a note that i don't want it to be build by using CMS system e.g Joomla or phpBB.