Bolt\Users::checkAvailability PHP Method

    public function checkAvailability($fieldname, $value, $currentid = 0)
    {
        foreach ($this->users as $user) {
            if ($this->canonicalizeFieldValue($fieldname, $user[$fieldname]) === $this->canonicalizeFieldValue($fieldname, $value) && $user['id'] != $currentid) {
                return false;
            }
        }
        // no clashes found, OK!
        return true;
    }