Hi James,
all the posts I've seen relating to this seem to ally with stuff I've seen regarding other package installations (like Joomla) and tend to point to you running Apache as a CGI install instead of an Apache module. You can read about elsehwere in these forums, but lets see if we can get a quick test going.
Create a file in your doc root - or another web addressable directory, call it something ambiguous, lets say test.php
put the following in it:
<?php
phpinfo();
?>
Now in some distros - OpenSuse and Redhat used to sometimes do this - phpinfo is a disabled function, you need to locate your php.ini file, look for 'disabled' and if its listed in there - take it out.
Save the file, then navigate to your site (and directory if you've used a sub-dir to your doc root) and test.php
When you get a bunch of info up in the browser - the third record line in Server API should say something like 'Apache 2.0 Handler' if you are running PHP as an Apache module.
Like this - hope the image loads!
Yea, looks like it did.
If it says CGI - then thats a fair indication of where stuff is going wrong.
If you are running on a Windows box with a default installer - like XAMPP or WAMP - they often use FastCGI to run and communicate between PHP and Apache. If you are in this boat (and indeed, even if you aren't) there's a neat little page at http://www.thesitewizard.com/php/install-php-5-apache-windows.shtml that goes into installing PHP as both CGI and Apache Module. The info is replicated in more detail on php.net somewhere, but I find that harder to locate.
hope this helps
Best wishes