public static function createSession($user_id)
{
//returns session string
$prfx = DB_PREFIX;
//test if session for user_id is already set
$open_session_rows = Data::getRow("SELECT * FROM {$prfx}session WHERE user_id={$user_id}");
$session_id = RequestUtils::random_str(24);
if (!$open_session_rows) {
//session for the user is NOT YET created
Data::submitModificationQuery("INSERT INTO {$prfx}session (session_id, user_id) VALUES ('{$session_id}', {$user_id})");
} else {
//session for the user is ALREADY created
Data::submitModificationQuery("UPDATE {$prfx}session SET session_id='{$session_id}' WHERE user_id={$user_id}");
}
return $session_id;
}
/**
* returns a temporary file for the problem with the specified id
* @param $id
* @return unknown_type
*/
function getTemporaryProblemFile()
{
return $GLOBALS['dces_dir_temp'] . '/' . RequestUtils::random_str(10) . '.problem';
}
