Plugin: WooCommerce - Set Virtual Order Status to Complete After Payment

functions.php

add_filter( 'woocommerce_payment_complete_order_status', 'webendev_virtual_order_payment_complete_order_status', 10, 2 );
/**
 * WooCommerce - Set Virtual Order Status to Complete After Payment
 *     http://www.skyverge.com/blog/how-to-set-woocommerce-virtual-order-status-to-complete-after-payment/
 *
 */
function webendev_virtual_order_payment_complete_order_status( $order_status, $order_id ) {
	$order = new WC_Order( $order_id );

	if ( 'processing' == $order_status &&
		( 'on-hold' == $order->status || 'pending' == $order->status || 'failed' == $order->status ) ) {

		$virtual_order = null;

			if ( count( $order->get_items() ) > 0 ) {

				foreach( $order->get_items() as $item ) {

					if ( 'line_item' == $item['type'] ) {

						$_product = $order->get_product_from_item( $item );

						if ( ! $_product->is_virtual() ) {
							// once we've found one non-virtual product we know we're done, break out of the loop
							$virtual_order = false;
							break;
						} else {
							$virtual_order = true;
						}
				}
			}
		}
		// virtual order, mark as completed
		if ( $virtual_order ) {
			return 'completed';
		}
	}
	// non-virtual order, return original status
	return $order_status;
}