Edited from /c admins in Gups
Warning: Not tested 
[pawn]      else if ( strcmp( cmd, "players", true ) == 0 )
   {
      new a, b[ 128 ], m = GetMaxPlayers() + 1;
      for ( a = 0; a < m; a++ )
      {
         if ( IsPlayerConnected( a ))
         {
             if ( strlen( b ) ) format( b, 128, "Total: [%d]: %s, %s",GetMaxPlayers(), b, gPlayers[ a ] );
            else format( b, 128, "%s", gPlayers[ a ] );
         }
      }
      if ( strlen( b ) )
      {
         format( szMsg, 128, "Players: %s, Total: [%d]", b, GetMaxPlayers() );
         SendClientMessageToAll( COLOR_YELLOW, szMsg );
      }
   }[/pawn]
Just add this on [pawn]onplayercommandtext[/pawn]