Try the following:
// Get the $order object from an ID (if needed only)
$order = wc_get_order( $order_id);
// Loop through order line items
foreach( $order->get_items() as $item ){
// get order item data (in an unprotected array)
$item_data = $item->get_data();
// get order item meta data (in an unprotected array)
$item_meta_data = $item->get_meta_data();
// get only All item meta data even hidden (in an unprotected array)
$formatted_meta_data = $item->get_formatted_meta_data( '_', true );
// Display the raw outputs (for testing)
echo '<pre>' . print_r($item_meta_data, true) . '</pre>';
echo '<pre>' . print_r($formatted_meta_data, true) . '</pre>';
}
Related: