GET and POST are not interchangeable and shouldn't be used as such. Proxy servers may cache the output of GET requests, browsers should prompt you if you hit refresh on a POST, and the two types are different. In practice, the only distinction that most notice is that POST requests are not logged, but GET requests are (since the query string is in the headers).

If you are using CGI.pm and need to use a POST but still have a query string embedded in the URL, open CGI.pm and look for the following:

      # Some people want to have their cake and eat it too!
      # Uncomment this line to have the contents of the query string
      # APPENDED to the POST data.
      # $query_string .= (length($query_string) ? '&' : '') . $ENV{'QU
+ERY_STRING'} if defined $ENV{'QUERY_STRING'};
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As a general rule of thumb, use GET when you *get* information from a server without changing it. Use POST when you *post* information to a server and thus change it. That's why we have two methods.

If you must mix and match methods, make sure that you don't use GET when you alter data on the server! Since browsers generally do not prompt on reload for a GET request, a user could inadvertently refresh a page and post data multiple times. Some browsers still allow this for a POST, but it's less common.

Cheers,
Ovid

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