[PHP-INSTALL] php returning completely empty documents on new apache install

[Matt G.]

I just built the latest apache 2.0 and php5 (shared apache module) on a linux 2.6.5 box.  After doing all of the setup from the INSTALL file, I'm unable to get a php hello world to work!  (Well, I get it to work with the CLI, but not through my web browser)  The apache server just returns a 0 byte document.  No errors come out in the apache logs and it says the document was sent with a http 200 status.  It is as if the php interpreter is not getting called. 

When the apache server starts up, it logs that php is in fact configured:

[Sat Mar 11 16:06:51 2006] [notice] Apache/1.3.34 (Unix) PHP/5.1.2 configured -- resuming normal operations

I believe I have the correct lines in my httpd.conf:
LoadModule php5_module        libexec/libphp5.so
AddModule mod_php5.c
    DirectoryIndex index.html index.php
AddType application/x-httpd-php .php .phtml
AddType application/x-httpd-php-source .phps


Does anybody have any suggestions for how I can dig into this further?