I just wanted to list this possibility for the error message when installing WP on a Mac localhost server:
"WordPress requires that your web server is running PHP. Your server does not have PHP installed, or PHP is turned off."
The Five Minute Install instructions do not spell out the installer has to access the install file with his browser by typing the local address in the address bar and not attempt to open it as a file. Also the address has to be entered exacting as:
http://localhost/site root directory/blog/wp-admin/install.php
The assumption is that the WP directory under the site root was named 'blog'