Woocommerce send SKU as item name to Paypal

<?php
function dp_change_name_to_sku ( $args, $order ) {
    $$args_keys = array_keys($args);
    $i = 0;
    // Iterating through order items
    foreach( $order->get_items() as $item_id => $item_product ){
    	$product_id = $item_product->get_product_id();
        $i++; // updating count.
        if( ! empty($args["item_name_$i"]) ){
            // getting sku of product
            $args["item_name_$i"] = get_post_meta($product_id, '_sku', true);
        }
    }

    return $args;
}
add_filter('woocommerce_paypal_args', 'dp_change_name_to_sku', 10, 2 );
?>