some_myuno_code.lua

local function inform_near_players(pos, msg)
	for _,player in pairs(minetest.get_objects_inside_radius(pos, 10)) do
		if player:is_player() then
			minetest.chat_send_player(player:get_player_name(), msg)
		end
	end
end

function apn(pos, placer, itemstack)
	local grop = minetest.get_item_group(minetest.get_node({x=pos.x, y=pos.y-1, z=pos.z}).name, "myuno")
	if group > 3 then
		return
	end

	local name = placer:get_player_name()
	if grop == 0 then
		minetest.chat_send_player(name, "You can not place a card there!")
		minetest.remove_node(pos)
		return itemstack
	end

	local node = minetest.get_node(pos)
	local descr = minetest.registered_items[node.name].description
	if grop == 1 then
		inform_near_players(pos, name.." placed a "..descr)
		return
	end

	minetest.set_node({x=pos.x, y=pos.y-1, z=pos.z}, node)
	minetest.remove_node(pos)
	if grop == 3 then
		return itemstack
	end

	inform_near_players(pos, name.." placed a "..descr)
end

Thanks for this. I tried it out. Seems to work great.