This is how I compile PHP as an Apache 2.x loadable module.

Since there's still no native Debian package supplying PHP for Apache 2.x, I built it myself. I haven't had the time nor the need to look up the build dependencies, but you'll notice soon enough when the configure process can't find certain libraries. Aparently I had them all readily installed.

./configure --enable-versioning --enable-memory-limit --with-layout=GNU \
     --disable-all --with-zlib-dir=/usr --with-regex=php --enable-bcmath \
     --with-bz2 --enable-calendar --with-cdb --enable-ctype --enable-dba \
     --enable-exif --enable-filepro --enable-ftp --with-gettext \
     --enable-mbstring --enable-mbregex --with-openssl --enable-overload \
     --with-pcre-regex=yes --enable-posix --enable-session --enable-shmop \
     --enable-sockets --enable-sysvsem --enable-sysvshm --enable-tokenizer \
     --with-expat-dir --with-zlib=yes --with-apxs2=/usr/bin/apxs2 \
     --with-gd=yes --with-mysql=yes --with-config-file-path=/etc \
	 --prefix=/usr

Notice that I don't use --with-openssl.
This 'flavour' of the PHP module will not run SquirrelMail when configured to do IMAPS, unless you recompile with --with-openssl

[update:20040718] Note that Debian's 'sid' distribution now comes with a 'libapache2-mod-php4' package that provides a well compiled loadable module for Apache2 setups.