Obtains a number guaranteed to be unique for the given
relation and will pass it back in the variable
A relation opened by dbplus_open().
Returns DBPLUS_ERR_NOERR on success or a db++ error code on failure.
This function is EXPERIMENTAL. The behaviour of this function, the name of this function, and anything else documented about this function may change without notice in a future release of PHP. Use this function at your own risk.