MCServerStatus
Query Minecraft servers for the online players, message of the day, and whether they're online or not.
Read more here: http://www.webmaster-source.com/2012/07/05/checking-the-status-of-a-minecraft-server-with-php/
Demo: http://www.webmaster-source.com/static/demos/mcserverstatus/
Requirements
- PHP 5.3+