Ajax who call php function and refresh information

Hello I want a script who Ajax call a php function on my web page have to refresh div with smarty to display in HTML on a <div> Example of use Show number of visitor : ajaxCallPHP(myPhpFunction, 10) i have already php function to count in mysql database I read on some forum to have to use XML HTTP request i need a html display and i use smarty i need 2 parametes in function : php_function_to_call and frequency_calling_php_function in seconds Can i use smarty to refresh only one div ? I don't want to reload my page. Don't hesitate to contact me if I'm at work i try to reply from my iphone if site is compatible