$("form").submit(function(){
	var room = $("input[name=roomid]").val();
    var button_id = $("input[type=submit]").attr("id");
    $.post("handler.php", { button_id: button_id, room: room }, function(data)){
    	alert(data);
    }
});

<form>
<input type='number' name='roomid'/><br>
<input type="submit"/>
</form>

if (isset($_POST['room'])){
    switch($_POST['room']){
        case 1:
            roomchange();
            break;
        default:
            errormsg();
            break;
}

function roomchange(){
    echo "Testje";
}
function errormsg(){
    echo "Error D:";
}