Looking For Free PHP Chat Scripts

Hi, everyone
I am looking for a free software where my website visitor can interact or chat with each other.They can send messages to each other on a pop up type or small screen while browsing my site. I want the software just a little pop up message that all visitors can see and reply to each other if they wish.
I am a php beginner, I found some php chat scripts listed on the page! But which one is suitable for me? And which one is best?
Any one point the right direction?
Thank you in advance!

Hello,

Well that's up to you, but here are some PHP variables you can use to your Forumotion forums:
https://help.forumotion.com/t48637-list-of-variables