here is solution

$referal_user = $request->ref;
    $referal_email = DB::table('admins')->where('mobile', $referal_user)->first();
    $referal_id = $referal_email->id;
    $right_count = $referal_email->no_user_right;
    $list_all_right_user = $referal_email->user_listing_right;
    $ref = $request->ref;
    $mobile = $request->mobile;
    $user_listing_left = $referal_email->user_listing_left;
    while( $refUser = Admin::where('mobile', $ref)->first() )
    {
        $refUser->user_left = $request->email;
        $refUser->user_listing_left = $refUser->user_listing_left . "," .$request->email;
        $refUser->save();

        // Update $ref to find the next guy
        $ref = $refUser->ref;

    }