_SERVER is http://
_SERVER['HTTP_HOST'] = websrv1.fenf.edu.uy
_SERVER['REQUEST_URI'] = /tildes.php
FULL URL (not decoded) = http://websrv1.fenf.edu.uy/tildes.php
FULL URL ( urldecoded) = http://websrv1.fenf.edu.uy/tildes.php
FULL URL (doble-urldecoded) = http://websrv1.fenf.edu.uy/tildes.php