Add docker container definition

Change-Id: If32020e6b8e8bb816eb54533554b18cc5302b5c9
diff --git a/php/change_password.php b/php/change_password.php
index 17d64bd..26cb709 100644
--- a/php/change_password.php
+++ b/php/change_password.php
@@ -6,7 +6,7 @@
 	Security::checkIsSignedIn();
 
 	$credentials = new Credentials();
-	$usersdb = $credentials->usersdb;
+	$usersdb = $credentials->usersdb();
 
 	date_default_timezone_set("Europe/Madrid");