if($session->userHasSession($user['id'])) {
throw new Exception('You can only have One session at a time. Please
wait for the other session to expire.');
}


public function userHasSession($user_id)
{
$this->cleanup();

// Check first, that the User exists on the Database
$query = 'select * from `users` where id = {user_id}';
$query_subst = array('user_id' => $user_id);
$mysqlres = mysqlConn::executeQuery($query, $query_subst);
if(mysql_num_rows($mysqlres) < 1) {
mysql_free_result($mysqlres);

// Block remaining operations, because the User is not valid on the
system
die("Exception: User requesting the Session is invalid!");

return false;
}

// Now, check if there is a Session for this User
$query = 'select * from `' . $this->table . '` where user_id =
{user_id}';
$mysqlres = mysqlConn::executeQuery($query, $query_subst);
if(mysql_num_rows($mysqlres) > 0) {
mysql_free_result($mysqlres);
return true;
} else {
mysql_free_result($mysqlres);
return false;
}
}

public function killSession()
{
if($this->started)
{
$query = 'DELETE FROM ' . $this->table . ' WHERE id =
{session_id}';
$query_subst = array('session_id' => $this->session_id);
if(mysqlConn::executeQuery($query, $query_subst))
{
set('session_id', '', time() - 259200);

return true;
}
}

return false;
}