(no version information, might be only in CVS)
Get the old value for the changed property
( void )
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.
Returns the old value for the changed property.
This can be used by a Data Access Service when
writing updates to a data source.
The DAS uses the old value to detect conflicts by comparing
it with the current value in the data source.
If they do not match, then the data source has been updated
since the data object was originally populated, and therefore
writing any new updates risks compromising the integrity of the data.