Followed the install procedure, but apache wont parse

I followed the install procedure to the letter for a statically linked mod_php4. I'm using apache 1.3.33 and php 4.3.11 on Mac OS X 10.3.9. The symptom is that if I use the standard AddType directives, apache just sends the source file to the browser, and the browser downloads it. If I take away the directly, it simply sends it as text/html. I know that mod_php4 is being loaded, because I've conditionalized the AddTypes in an IfModule directive. I've been banging my head over this for hours, reading every post I could from anyone out there on the subject, but there's never any advice beyond adding the mime type. Understandably, I'm rather frustrated. I've checked my logs, I've restarted apache dozens of times, each time trying a different permutation of directives. If anyone could help, it'd be much appreciated. Thanks, James