Comment 3 for bug 1890263

There seem to be two different ways of installing modphp:

  1. sudo apt-get install libapache2-mod-php
or
  2. sudo apt-get install libapache2-mod-php7.2

libapache2-mod-php is a virtual package that depends on the appropriate libapache2-mod-phpN.M for that Ubuntu release; presumably if one had installed libapache2-mod-php the upgrade should work seamlessly. However, if one rather installed libapache2-mod-php7.2, then I think this is where the bug presents itself.

Furthermore, there's multiple upgrade methods to consider:

  A. Running `do-release-upgrade -d`
  B. Editing /etc/apt/sources.list from bionic -> focal (or focal -> jammy, or impish -> jammy)
  C. Upgrading just modphp itself via a PPA

Method C is presumably how most users would be experiencing this, so the main one needing fixed, but it's also the most time-intensive to test. #2 is easier to test and still conceivably used by some experienced users, so is worth getting right. #3 is easiest to test but pretty artificial (though php users are accustomed to upgrading php via ondrej's ppa).

We see that in each of these cases, libapache2-mod-php7.2 might be left in place, or removed as cleanup.