First steps of newbie in CI.

PHP Code:

$referrred      =   getReferreds($email_new_user); 


This line doesn't do anything (assuming you haven't declared a global scope function called getReferreds.)

You could do it like:

PHP Code:

$referredsModel = new ReferredsModel();
$referred = $referredsModel->getReferreds($email_new_user);
$id_ref = $referred['referreds']['id_referred'] ?? 5; 


If that doesn't work, you'd need to show the code for getReferreds method in ReferredsModel.