Comment 9 for bug 1076489

You are very likely right.
I tried to test a web application which needed a number of php5 stuff to be pulled.
Once I decided the tests were over, I tried to uninstall those packages.
The end situation was the one I described.

php5-cgi says:
Description-en: server-side, HTML-embedded scripting language (CGI binary)
 This package provides the /usr/lib/cgi-bin/php5 CGI interpreter built
 for use in Apache 2 with mod_actions, or any other CGI httpd that
 supports a similar mechanism. Note that MOST Apache users probably
 want the libapache2-mod-php5 package.
 The following extensions are built in: bcmath bz2 calendar Core ctype date
 dba dom ereg exif fileinfo filter ftp gettext hash iconv json libxml
 mbstring mhash openssl pcntl pcre Phar posix Reflection session shmop
 SimpleXML soap sockets SPL standard sysvmsg sysvsem sysvshm tokenizer wddx
 xml xmlreader xmlwriter zip zlib.

apache2 says:
Description-en: Apache HTTP Server metapackage
 The Apache Software Foundation's goal is to build a secure, efficient and
 extensible HTTP server as standards-compliant open source software. The
 result has long been the number one web server on the Internet.
 .
 It features support for HTTPS, virtual hosting, CGI, SSI, IPv6, easy
 scripting and database integration, request/response filtering, many
 flexible authentication schemes, and more.

I don't really understand from the descriptions how they are mutually exclusive, as seen in my 1st post.
Moreover, if one of them requires php5, that package should get expunged along with them, whichever I ask to uninstall.