Ajax RPG Game Map - With PHP and SQL (a push in the right direction)

Just need someone to show me in what area I should start looking todo this 

just need a helping hand to start on the basic 

I would like to have an Ajax based map, where the player explore the maps ( yeah, serveral maps like plains, dungeons, lakes.. etc ).

Imagine a Pokemon Game for example. The user plays around the field and when it is in specific points, then turn up a button where they can perform some actions that will call the coding for  battles  

IE the game map below

http://static.monstermmorpg.com/images/Screenshots/EN/GamePage.png

Thanks once again