You must proper set up your apache first . I assume you are using a .htaccess file , if you remove it and acess index.php and get some php errors ( it would be normal) , it's because of improper apache configuration( I assume you are not using php cgi ).
Ensure mod_rewrite is loaded in your apache , if so , make sure AlowOverides is set to all for your web directory so that your .htaccess file can be effective and also FollowSymlinks option is present .
You may want to check :
Apache Tutorial: .htaccess files - Apache HTTP Server
and
Blueprint for PHP Applications: Bootstrapping (part 2) , and if this does not help and apache seems the problem I will help you further.
Regards