help script ranks per vocation!

[aioriusox]

!top kina 
!top pala

local tops = { 
['None'] = {0}, 
['Sorcerer'] = {1}, 
['Druid'] = {2}, 
['Paladin'] = {3}, 
['Knight'] = {4}, 
['Master Sorcerer'] = {5}, 
['Elder Druid'] = {6}, 
['Royal Paladin'] = {7}, 
['Elite Knight'] = {8}, 
} 
function onSay(cid, words, param, channel) 
local msg = string.lower(param) 
if tops[msg] ~= nil then 
str = getVocationInfo((tops[msg][1])) 
else 
str = getVocationInfo((0)) 
end 
doShowTextDialog(cid,7873, str) 
return TRUE 
end

the script has to show the rank of knight level to see where the strongest knight, which druid, pala which wanted to know which function to use and how to use.
wanted help with this function.

I type the following happens! top knight and nothing appears in the window that opens to show rank. How can I do to fix this?