$host = $SERVER['HTTP_HOST'];
$req_uri = $SERVER['REQUEST_URI'];
$scr_name = $SERVER['SCRIPT_NAME'];
$php_self = $SERVER['PHP_SELF'];

// 1
$url1 = $host . $req_uri;
// 2
$url2 = $host . $scr_name;
// 3
$url3 = $host . $php_selfi;

ケースバイケースで好きなのを選べ