Save a SESSION array in database and read it out

Question

ich want to save my SESSION in my databese. For this I used this code:

 $sql = "INSERT INTO
                 bestellung
                (b_nutzer_id
                 b_artikel_id,
                 b_bestellte_anzahl,
                 b_bestelldatum,
                 b_zahlungsart_id
                )
        VALUES
                ('".mysqli_real_escape_string($verbinde, trim($_SESSION['login']))."',
                 '".mysqli_real_escape_string($verbinde, trim($_SESSION['warenkorb']['warenkorb_id']))."',
                 '".mysqli_real_escape_string($verbinde, trim($_SESSION['warenkorb']['menge']))."',
                 '".mysqli_real_escape_string($verbinde, trim(time()))."',
                 '".mysqli_real_escape_string($verbinde, trim($_SESSION['Zahlart']))."'
                )
       ";
        mysqli_query($verbinde, $sql) OR die(mysqli_error($verbinde));

This is the content of my array:

Array ( [0] => Array ( [warenkorb_id] => 7 [menge] => 4 ) [1] => Array ( [warenkorb_id] => 7 [menge] => 1 ) ) 

I always get the error that my array is undefinded. After I did this I want to show the content of the database on another place on the website. What am I doing wrong?

I would be really happy, if somenone could help me :)