[SnG.Scot_MisCuDI]

PHP код:

#include <sscanf2>
CMD:changemission(playerid, params[])
{
    if(IsPlayerAdmin(playerid)
    {
        new mission[50], cmd[50]; //strings
        if(sscanf(params, "s", mission)) return SendClientMessage(playerid, -1, "USAGE: /changemission (mission)"); //if playerid doesnt type in mission name playerid will get error message
        format(cmd, sizeof(cmd), "changemode %s", mission); //formatting the string to be used in SendRconCommand
        SendRconCommand(cmd); //calling the command and changing the gamemode     
    }
    return 1;
} 


Links:
sscanf2 (needed to use code): https://sampforum.blast.hk/showthread.php?tid=570927
SendRconCommand: https://sampwiki.blast.hk/wiki/SendRconCommand