your error message is somewhat different from the one discussed in the thread you’ve linked. My guess is that in your case the package
php5-common was removed but not purged. Verify this by running the following:
dpkg -l php5-common
The first two columns indicate the package status. If it’s
rc (= removed, configured), it means that it has been removed, but the the configuration files are still present, and those include the cron job. Purging the package with
dpkg --purge php5-common should get rid of the cron job, too.
It’s good practice to purge all packages in status “removed, configured” regularly anyway (after making sure you don’t need the content of the configuration files anymore) — at least before each big upgrade such as from 4.2-3 to 4.3-0.