Add docker container definition

Change-Id: If32020e6b8e8bb816eb54533554b18cc5302b5c9
diff --git a/php/db.php b/php/db.php
index 2043b87..1291b10 100644
--- a/php/db.php
+++ b/php/db.php
@@ -3,7 +3,7 @@
 
 // Create connection
 $credentials = new Credentials();
-$conn = new mysqli($credentials->servername, $credentials->username, $credentials->password, $credentials->dbname);
+$conn = new mysqli($credentials->servername(), $credentials->username(), $credentials->password(), $credentials->dbname());
 
 if ($conn->connect_error) die("Connection failed: " . $conn->connect_error);
 $conn->set_charset("utf8");