Printing an HTML document using format/2
is not a neat way of producing HTML because it is vulnerable to required
escape sequences. A high-level alternative is provided by
from the HTTP library.
The startup-time of Prolog is relatively long, in particular if the program is large. In many cases it is much better to use the SWI-Prolog HTTP server library and make the main web-server relay requests to the SWI-Prolog webserver. See the SWI-Prolog HTTP package for details.
The CGI standard is unclear about handling Unicode data. The above two declarations ensure the CGI script will send all data in UTF-8 and thus provide full support of Unicode. It is assumed that browsers generally send form-data using the same encoding as the page in which the form appears, UTF-8 or ISO Latin-1. The current version of cgi_get_form/1 assumes the CGI data is in UTF-8.