To launch if, you just need to set the listen address and pages folder, for example:

$ php -S 127.0.0.1:8080 -t /work/GLPI/0.83-bugfixes
PHP 5.4.0RC4-dev Development Server started at Sat Dec 17 09:39:11 2011
Listening on 127.0.0.1:8080
Document root is /var/www/html
Press Ctrl-C to quit.

Then, from your browser: http://127.0.0.1:8080/

$_SERVER["SERVER_SOFTWARE"] => PHP 5.4.0RC4-dev Development Server

Useful, don't you think ?

Documentation : Built-in web server

Of course, this is only for development, not designed for anything else.