[IceBilizard]

why you are using r for userid?

PHP Code:

if(sscanf(params, "u", id)) return SCM(playerid, COLOR_GRAD2, "Usage: {FFFFFF}/tradecar [playerid] + [difference]"); 


for user you must use u read about sscanf here
https://sampwiki.blast.hk/wiki/Sscanf_code