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. The variable player is nil because nothing ever filled it, so reading player.name is a nil error waiting to happen. This is the most common error you will ever see.

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. Now open txAdmin in your browser (default address http://localhost:40120), log in, and open the Live Console from the left menu - that is where you type server commands and read this lesson's output. Run this there:

restart qu_debug_class

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

Before guessing, prove it. Add print(type(value), value) on the line before the crash. This one line answers almost every nil mystery. 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 ' .. tostring(player and 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.