I think the problem lies somewhere else. Try to debug your code with debug functions.
Also check this:
addEventHandler("s_callback", root, function()
triggerServerEvent("serverCallback", localPlayer, s_tarek) -- ????
Thank you @stPatrick. The first method did work, but the method you said was much more simpler, did not work. No errors in debug.
Thanks @IIYAMA. But I thought I had assigned a value to it here,
c_tarek = s_tarek
addEventHandler("getClientTarekElement", root, getClientTarekElement_func)
I still don't understand why c_tarek would not be recognised in any other function.