(PECL mongo >= 1.0.1)
MongoTimestamp::__construct — Creates a new timestamp.
$sec = time()
   [, int $inc
  ]] )Creates a new timestamp. If no parameters are given, the current time is used and the increment is automatically provided. The increment is set to 0 when the module is loaded and is incremented every time this constructor is called (without the $inc parameter passed in).
sec
     Number of seconds since the epoch (i.e. 1 Jan 1970 00:00:00.000 UTC).
inc
     Increment.
Returns this new timestamp.