(mongodb >=1.3.0)
MongoDB\BSON\TimestampInterface::getTimestamp — Returns the timestamp component of this TimestampInterface
此函数没有参数。
Returns the timestamp component of this TimestampInterface.
On 32-bit systems this method may return a negative number. Although the increment and timestamp parts of the BSON timestamp type consists of two unsigned 32-bit values, PHP can not represent these on 32-bit platforms.