code below require_once does not execute - php

Question

I have following code, however $email is not getting printed on page. I don't know why.
<?php
$email = "myemil#gmail.com";
$tag = "login";
require_once 'DB_Functions.php';
$db = new DB_Functions();
echo $email;
?>
If I remove
require_once 'DB_Functions.php'; $db = new DB_Functions();
then it prints email on page. Why is this happening? I want to connect to DB. Please help.
Above code file is on godaddy server, in a subdomain.
DB_Functions.php looks like
class DB_Functions {
private $db;
function __construct() {
require_once 'DB_Connect.php';
$this->db = new DB_Connect();
$this->db->connect();
}
function __destruct() {
}
}
DB_Connect looks like
class DB_Connect {
// constructor
function __construct() {
}
// destructor
function __destruct() {
// $this->close();
}
// Connecting to database
public function connect() {
require_once 'config.php';
// connecting to mysql
$con = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
// selecting database
mysql_select_db(DB_DATABASE);
// return database handler
return $con;
}
// Closing database connection
public function close() {
mysql_close();
}
}
config.php
define("DB_HOST", "localhost");
define("DB_USER", "db1");
define("DB_PASSWORD", "db1");
define("DB_DATABASE", "db1");