[Dismounted]

The only thing you (really) need to know for AJAX apart from coding the PHP response and basic Javascript is this little piece of code:

YAHOO.util.Connect.asyncRequest('POST', scriptpath + '?do=ajax', {
	success: this.handle_ajax_response,
	failure: this.handle_ajax_error,
	timeout: vB_Default_Timeout,
	scope: this
}, SESSIONURL + 'securitytoken=' + SECURITYTOKEN + '&foo=' + foo);