WooCommerce: Create XML file on order completion

I’m trying to export XML, when order is complete. I’m facing a problem. Everything works well, but the XML isn’t exported to the folder, if I remove this statement:

if ( ( ( $order->payment_method_title ) == "Cash on delivery" ) )

The checkout will break and say that unable to make the order try again, but the XML is exported!

This is my function:

//Woocommerce hook to generate an xml file when the order is completed.
//____________________________________________________________________

add_action( 'woocommerce_checkout_order_processed','woocommerce_xmlCreation' );
function woocommerce_xmlCreation( $order_id ) {
    $order = new WC_Order( $order_id );
    if ( ( ( $order->payment_method_title ) == "Cash on delivery" ) ) {
        xmlCreate( $order_id );
        upload( $order_id );
    }
}

add_action( 'woocommerce_payment_complete','woo_xmlCreate' );
function woo_xmlCreate( $order_id ) {
    xmlCreate( $order_id );
    upload( $order_id );
}

add_action( 'woocommerce_thankyou','uploadedState' );
function uploadedState() {
    session_start();
    global $uploaded;
    return $uploaded;
}

Thank you for you time.