PHP5 test file downloads instead of displaying in browser

[adp]

I installed PHP5 using Macports on my macbook running OS X 10.5.5 with variants +apache2 +mysql5 +pear using instructions I found at the site below.

http://2tbsp.com/content/install_apache_2_and_php_5_macports

Apache2 and mysql5 are already installed.

When I went to http://localhost/test.php (using Safari 3.1.2), the test file itself downloaded automatically instead of displaying the message I had expected. No text appeared on the screen.

I had just uninstalled a previous macport of PHP5 because of problems linking to mysql5 that had remained unsolved. Any chance there is vestigial text in some file that might cause the problem?
Something in php.ini or httpd.conf mistyped or missing?

Thanks in advance for any suggestions.