Fix 2Checkout.com

Hello. I try to get order number after payment. So on this line: if ($charge['response']['responseCode'] == 'APPROVED') { I tried to add $charge['response']['orderNumber'] But no success it only adds { How i can get that order number? The Json result is : stdClass Object ( [validationErrors] => [response] => stdClass Object ( [type] => AuthResponse [currencyCode] => USD [lineItems] => Array ( [0] => stdClass Object ( [description] => [duration] => [options] => Array ( ) [price] => 12 [quantity] => 1 [recurrence] => [startupFee] => [productId] => [tangible] => N [name] => 40 [type] => product ) ) [transactionId] => 106249471627 [billingAddr] => stdClass Object ( [addrLine1] => [addrLine2] => [city] => [zipCode] => [phoneNumber] => [phoneExtension] => [email] => [country] => [name] => [state] => ) [shippingAddr] => stdClass Object ( [addrLine1] => [addrLine2] => [city] => [zipCode] => [phoneNumber] => [phoneExtension] => [email] => [country] => [name] => [state] => ) [merchantOrderId] => 40 [orderNumber] => 106249471618 [recurrentInstallmentId] => [responseMsg] => Successfully authorized the provided credit card [responseCode] => APPROVED [total] => 12.00 [errors] => ) [exception] => )