[Scenario]

If I were you, I would consider using SSCANF(2) and ZCMD. This is the command using SSCANF(2), but not ZCMD.

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(!strcmp("/o", cmdtext, true, 2))
    {
        new message, string[128], sendername[24];
        if(sscanf(params, "s[105]", message)) return SendClientMessage(playerid, COLOR_WHITE, "SYNTAX: /o [message]");
        GetPlayerName(playerid, sendername, sizeof(sendername));
        format(str, sizeof(str), "OOC %s: %s", sendername, message);
        SendPlayerMessageToAll(playerid, str);
        return 1;
    }
    return 0;
}

It should work for you.

EDIT: I am so used to working with ZCMD that the command I provided for you will not work with STRCMP. I'll see what I can do, as I don't use STRCMP. I would recommend that you use ZCMD and convert your STRCMP commands to ZCMD as "OnPlayerCommandText" will cause a compatibility issue.