Make sure that when configuring php, you have to use the '--with-apxs2=/location/of/apache 2/apxs' option.
My installation on linux went like this with PHP 5.1 and Apache 2.0.55:
1) unpacked both php and apache into their appropriate directories.
2) went into the apache directory and did the following configure:
# ./configure --enable-module=so --prefix=/var/www
<stuff here>
# make
# make install
3) backed out and went into my php directory and did the following configure:
# ./configure --with-pgsql=/db [color=red]--with-apxs2=/var/www/bin/apxs[/color] --with-png --with-gd --with-jpeg-dir=/usr
# make
<stuff here>
# make test
<stuff here>
# make install
<more stuff>
# cp php.ini-recommended /usr/local/lib/php.ini
The php configuration I did enabled png graphics with gd implementation, PostgreSQL support, and integration into Apache 2's config file (httpd.conf).
In your httpd.conf file, you need to make sure of a few things.
The lines below need to be put somewhere in the file (I put mine right after the Listen statement):
[!--quoteo--][div class=\'quotetop\']QUOTE[/div][div class=\'quotemain\'][!--quotec--]
LoadModule php5_module modules/libphp5.so
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
Modify the line of your DirectoryIndex to include php files. Mine's like this:
[!--quoteo--][div class=\'quotetop\']QUOTE[/div][div class=\'quotemain\'][!--quotec--]
DirectoryIndex index.php index.html
And that's it. Start up your webserver and test it out. On my command prompt, I do this:
# php -r 'echo phpinfo();'
<same info as you would see in a php test file appears here>