- It is more secure. The PHP runs as your user rather than dhapache. That means you can put your database passwords in a file readable only by you and your php scripts can still access it!
- It is more flexible. Because of security concerns when running PHP as an Apache module (which means it runs as our dhapache user), we have disabled a number of commands with the non-CGI PHP. This will cause installation problems with certain popular PHP scripts (such as Gallery) if you choose to run PHP not as a CGI!
- It's just as fast as running PHP as an Apache module, and we include more default libraries.
- Custom 404 pages won't work for .php files with PHP-CGI. Or will they? See n74's comment below!
- Variables in the URL which are not regular ?foo=bar variables won't work without using mod_rewrite (http://httpd.apache.org/docs/mod/mod_rewrite.html) (example.com/blah.php/username/info/variable).
- Custom php directives in .htaccess files (php_include_dir /home/user;/home/user/example_dir) won't work.
- The $_SERVER['SCRIPT_NAME'] variable will return the php.cgi binary rather than the name of your script
- Persistant database connections will not work. PHP's mysql_pconnect() function will just open a new connection because it can't find a persistant one.
If one of those is a show-stopper for you, you can easily switch to running PHP as an Apache module and not CGI, but be prepared for a bunch of potential security and ease-of-use issues! If you don't know what any of these drawbacks mean, you're fine just using the default setting of PHP-CGI and not worrying about anything!
