echo $_SERVER['HTTP_HOST']; #localhost

echo $_SERVER['PHP_SELF']; #/PHP/XX.php

echo $_SERVER["QUERY_STRING"]; #id=5

echo $_SERVER['HTTP_REFERER']; 

echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
echo 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'].'?'.$_SERVER['QUERY_STRING'];
#http://localhost/PHP/XX.php?id=5

echo 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER["SERVER_PORT"].$_SERVER["REQUEST_URI"];
#http://localhost:80/PHP/XX.php?id=5

$url='http://'.$_SERVER['SERVER_NAME'].$_SERVER["REQUEST_URI"]; 
echo dirname($url);
#http://localhost/PHP