Invoice Line Retrieval

$customer_id = $event_json->data->object->customer;
$customer = \Stripe\Customer::retrieve($customer_id);
$email = $customer->email;
$invoice_id = $event_json->data->object->id;
$invoice = \Stripe\Invoice::retrieve($invoice_id);
$amount_due = $invoice->amount_due / 100;
$stripe_subscription_id = $invoice->subscription;
$stripe_invoice = $invoice->id;
$amount_due_gbp = sprintf("%.2f", $amount_due);
$invoice_lines = $invoice->lines->all();
$amt_line = printf("%.2f", $amt / 100);

//loop to get variables from the array
$des = array();
$amt_line = array();
foreach ($invoice_lines->data as $line) {
$des[] = $line['description'];
$amt_line[] =  $line['amount'] / 100 ;
}