Debug class for total beginners

Make the resource folder

Inside your server's resources folder - the resources folder lives in your FXServer data/base folder, the same place that contains your server.cfg - create this folder:

resources/qu_debug_class

Create the files

Create this exact file layout:

resources/qu_debug_class/
fxmanifest.lua
server.lua

Write fxmanifest.lua

Open fxmanifest.lua and paste this. Lua 5.4 is the only runtime in 2026, so there is no lua54 line to add. Leave it out.

fx_version 'cerulean'
game 'gta5'
 
server_script 'server.lua'

Break it on purpose

Open server.lua and paste this on your test server. The variable player is nil because nothing ever filled it, so reading player.name will produce a nil error when you run the command.

RegisterCommand('debugclass', function()
local player = nil
print('[qu_debug_class] name is ' .. player.name)
end, true) -- final `true` = restricted: only principals with ACE permission (e.g. the server console / admins) may run it, so a normal player cannot trigger this command

Start it and trigger the error

Open server.cfg and add this line:

ensure qu_debug_class

Save. Open your server's txAdmin address, log in, and open the Live Console. The default http://localhost:40120 works when your browser is on the same machine as txAdmin; a remote VPS needs your configured administrator connection. Run these commands there, one at a time:

refresh
ensure qu_debug_class

refresh discovers the new resource and its manifest. ensure starts it, or restarts it if it is already running. Adding a line to server.cfg does not execute that line in a running server. Confirm there is no startup error before continuing. Now run the command:

debugclass

You will see a SCRIPT ERROR. Read only the first red line. It names the file (server.lua), the line number (3), and the missing thing (player).

Translate the error into plain English

nil means "there is nothing here." It becomes an error only when you use the nothing like it was real data or a real function. There are four you will meet constantly:

attempt to index a nil value         -> you read thing.name on an empty thing
attempt to call a nil value          -> you ran thing() but thing is not a function
attempt to concatenate a nil value   -> you glued text onto an empty value
attempt to perform arithmetic on nil -> you did math (+ - * /) on an empty value

Yours says index a nil value (local 'player'). So stop asking "why is Lua broken?" and ask "what value did I assume existed here?" The answer is player.

Confirm it with the fastest debug tool

Add print(type(player), player) immediately before the failing access. Keep the original access in place so you can see the diagnostic output followed by the same failure. Edit server.lua to this:

RegisterCommand('debugclass', function()
local player = nil
print('[qu_debug_class] type check', type(player), player)
print('[qu_debug_class] name is ' .. player.name)
end, true)

Then restart qu_debug_class and run debugclass again.

Fix the one thing and test again

The fix is to give player a real table with a name key, instead of nil. Change server.lua to this and restart cleanly:

RegisterCommand('debugclass', function()
local player = { name = 'Los Santos' }
print('[qu_debug_class] type check', type(player), player)
print('[qu_debug_class] name is ' .. player.name)
end, true)

Run restart qu_debug_class, then debugclass. No red line, and the name prints. You read the first error, found the file and line, named the missing value, proved it, and fixed exactly one thing.