Torsten, php5-common was purged in my case, because it was picked instead of php5-mhash.
The repository layout and dependencies have probably changed since 10.04, but the point is:
If package A gets removed (not purged), and you later want to purge it, the purge action should not pick package B which provides A.
It is just like "apt-get remove A" should never remove B, in case A is not installed.
Torsten, php5-common was purged in my case, because it was picked instead of php5-mhash.
The repository layout and dependencies have probably changed since 10.04, but the point is:
If package A gets removed (not purged), and you later want to purge it, the purge action should not pick package B which provides A.
It is just like "apt-get remove A" should never remove B, in case A is not installed.