[=KempeR=]

Better realisation, without using timers

PHP код:

new commandShopUsed[MAX_PLAYERS];
#define commandShopInterval 3600 //in seconds
CMD:shop(playerid) {
    if (gettime() < commandShopUsed[playerid])
        return SendClientMessage(playerid, -1, "Please Wait to use this command again");
    commandShopUsed[playerid] = gettime() + commandShopInterval;
    //Common code starts here
    return true;
} 


You can save commandShopUsed[playerid] to player's account