Updating wordpress user meta data array (unexpected multiple arrays)

Question

So I am trying to update a user meta data array that I have previously stored with this function:

function oe_charge_customer( $customer ) { 

    // load the stripe libraries
    require_once(STRIPE_BASE_DIR . '/lib/Stripe.php');

    // check if in test mode or not
    check_stripe_api();

    // counter
    $i = $customer['i'];

    // get user meta, if any
    $payment_args = get_user_meta( $customer['user_id'], 'oe_customer_details' );

    // update paid value to true
    $payment_args[0]['payments'][$i]['paid'] = 1;

    // attempt to charge the customer's card
    try {

        $charge = Stripe_Charge::create(array(
                'amount'    => $customer['amount'] * 100,
                'currency'  => 'usd',
                'customer'  => $customer['cust_id']
            )
        );

        // update user profile to show paid
        update_user_meta( $customer['user_id'], 'oe_customer_details', $payment_args );

    } catch (Exception $e) {

        wp_die($e);

    }

}

I am getting somewhat expected results, except it keeps throwing it in a new array every time it gets updated. Any idea why this is happening? I can't seem to wrap my head around it . I get the following after it gets updated:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => Array
                        (
                            [0] => Array
                                (
                                    [0] => Array
                                        (
                                            [customer] => Array
                                                (
                                                    [name] => 
                                                    [id] => cus_2Oo1hyvYyZsaj0
                                                    [user_id] => 18
                                                )

                                            [payments] => Array
                                                (
                                                    [0] => Array
                                                        (
                                                            [amount] => 16
                                                            [date] => 1376710188
                                                            [paid] => 0
                                                        )

                                                    [1] => Array
                                                        (
                                                            [amount] => 4
                                                            [date] => 1376710238
                                                            [paid] => 0
                                                        )

                                                )

                                        )

                                    [payments] => Array
                                        (
                                            [0] => Array
                                                (
                                                    [paid] => 0
                                                )

                                        )

                                )

                        )

                    [payments] => Array
                        (
                            [1] => Array
                                (
                                    [paid] => 1
                                )

                        )

                )

        )

)

Answer 1

It looks like get_user_meta() returns an array like such.

array(2) {
   [0]=>
       array(1) {
           [0]=>
       }

   [1]=>
       array(1) {
           [0]=>
       }
}

Then when update_user_meta() stores the array it sticks it inside another array like this.

Edit: As it turns out get_user_meta() is encapsulating the result in an array when it grabs it.

array(1) {
    [0]=>
        array(2) {
           [0]=>
               array(1) {
                   [0]=>
               }
           [1]=>
               array(1) {
                   [0]=>
               }
        }
}

Then later it's retrieved and saved again adding a new level each time.

There's a simple, although counter-intuitive, solution to this problem. Set the last parameter of get_user_meta() to true.

get_user_meta($id,$key,true);`

If it is false it returns an array and if it is true it returns a single value which could be an array itself.

More info is available here. https://stackoverflow.com/questions/7746887/storing-php-arrays-in-wordpress-user-meta-database