How to send API call once an order received

I want to send an API call to a third-party URL outside the website domain when an order is received. Therefore I tried this code to send the details I required to send.

// Register a custom AJAX endpoint
add_action('wp_ajax_process_order_received', 'process_order_received');
add_action('wp_ajax_nopriv_process_order_received', 'process_order_received');
function process_order_received() {
    if (isset($_POST['order_id'])) {
        $order_id = intval($_POST['order_id']);

        // Get the order object
        $order = wc_get_order($order_id);

        // Get the customer details
        $first_name = $order->get_billing_first_name();
        $last_name = $order->get_billing_last_name();
        $email_address = $order->get_billing_email();

        // Get the product details
        $items = $order->get_items();
        $item = reset($items);
        $product = $item->get_product();
        $product_name = $product->get_name();
        $product_sku = $product->get_sku();

        // Get the order status
        $order_status = $order->get_status();

        // Get the order totals
        $regular_price = $order->get_total();
        $selling_price = $order->get_total();

        // Log the data for debugging purposes
        error_log('Order ID: ' . $order_id);
        error_log('First Name: ' . $first_name);
        error_log('Last Name: ' . $last_name);
        error_log('Email Address: ' . $email_address);
        error_log('Product Name: ' . $product_name);
        error_log('Product SKU: ' . $product_sku);
        error_log('Order Status: ' . $order_status);
        error_log('Regular Price: ' . $regular_price);
        error_log('Selling Price: ' . $selling_price);

        // Send AJAX API call
        $api_url = 'https://thirdpartywebsite/api/api.php';
        $data = array(
            'order_id' => $order_id,
            'first_name' => $first_name,
            'last_name' => $last_name,
            'email_address' => $email_address,
            'product_name' => $product_name,
            'product_sku' => $product_sku,
            'order_status' => $order_status,
            'regular_price' => $regular_price,
            'selling_price' => $selling_price,
        );

        $response = wp_remote_post($api_url, array(
            'body' => $data,
            'timeout' => 45,
            'sslverify' => true,
        ));

        if (!is_wp_error($response)) {
            // Handle the API response if needed
            $response_code = wp_remote_retrieve_response_code($response);
            $response_body = wp_remote_retrieve_body($response);
            // Process the response as required

            // Log the API response for debugging purposes
            error_log('API Response Code: ' . $response_code);
            error_log('API Response Body: ' . $response_body);
        }
    }

    // Always die or exit at the end of an AJAX callback
    die();
}

And the ajax function

add_action('woocommerce_checkout_update_order_meta', 'send_order_details_ajax');
function send_order_details_ajax($order_id) {
    // Get the order ID from $_POST
    if (isset($_POST['order_id'])) {
        $order_id = $_POST['order_id'];
    }

    // Get the order object
    $order = wc_get_order($order_id);

    // Get the customer details
    $first_name = $order->get_billing_first_name();
    $last_name = $order->get_billing_last_name();
    $email_address = $order->get_billing_email();

    // Get the product details
    $items = $order->get_items();
    $item = reset($items); // Assuming there is only one item in the order
    $product = $item->get_product();
    $product_name = $product->get_name();
    $product_sku = $product->get_sku();

    // Get the order status
    $order_status = $order->get_status();

    // Get the order totals
    $regular_price = $order->get_total();
    $selling_price = $order->get_total();

    // Send AJAX request
    $data = array(
        'order_id' => $order_id,
        'first_name' => $first_name,
        'last_name' => $last_name,
        'email_address' => $email_address,
        'product_name' => $product_name,
        'product_sku' => $product_sku,
        'order_status' => $order_status,
        'regular_price' => $regular_price,
        'selling_price' => $selling_price,
    );

    wp_send_json($data);
}

This when we tried to echo json_encode($data); the data getting output as NULL.

How to manage this in WooCommerce, please?