libphp4.so does not have a corresponding .info file

[Marc <debian@roth.lu>]

Hi there,
I am running an Apache 1 (the Debian package) with a self-compiled PHP
module (because some customer needed PHP 4.3.x).
Now I wanted to install the WebDAV module (also the Debian package) and
it gave me the error in the subject. (Obviously it is Apache that is
somehow complaining about my custom PHP module)
But since now I found out I don't actually need it, I wanted to get rid
of the WebDAV module again (that did not install in the first place) using

# apt-get remove --purge libapache-mod-dav

and that doesn't work either. Why does it care during removal? :

Removing libapache-mod-dav ...
Error: libphp4.so does not have a corresponding .info file.
The above errors might cause apache to not work properly or start
Please refer to the documentation on how to fix it or report it to
Debian Apache Mailing List <debian-apache@lists.debian.org> if in doubt
on how to proceed
dpkg: error processing libapache-mod-dav (--remove):
 subprocess post-removal script returned error exit status 20
Errors were encountered while processing:
 libapache-mod-dav
E: Sub-process /usr/bin/dpkg returned an error code (1)

Regards,
Marc