/**
  * 
  * @param integer $user_id
  * @param integer $act_id
  * @param float $value
  * @param boolean $monetary
  */
 public static function createAccountUser($user_id, $account_id)
 {
     /* ------- ACCOUNT_USER CREATION ------- */
     //In order to link the user and the account, we need a AccountUser object:
     $account_user = new AccountUser();
     //Set its values:
     $account_user->setUserId($user_id);
     $account_user->setAccountId($account_id);
     //Save it:
     $saved_account_user = $account_user->save();
     return $account_id;
 }