You can't alter clientr. variables from clientside. You can, however, alter client. variables clientside but these types are far less secure. It depends on your need, really.
Anyways, this is how you can alter a clientr. variable
PHP Code:
function onActionServerSide() {
if (params[0] == "test") {
clientr.variable = 1;
}
}
//#CLIENTSIDE
function GuiButton.onAction() {
triggerserver("gui", this.name, "test");
}