Custom Webhook results not in array

I have created an action to send data after an order is completed in WooCommerce. I have added the following code to the functionc.php file. I works, but the raw data is showing as: billingemail=sub%40imedi.co.za&items%5B90%5D=14-day+Free+Trial and I need it as a json array.

add_action( ‘woocommerce_order_status_completed’, ‘my_function’ );
/*
* Do something after WooCommerce set an order status as completed
*/
function my_function($order_id) {

// order object (optional but handy)
$order = new WC_Order( $order_id );
$billingEmail = $order->billing_email;
$products = $order->get_items();

foreach($products as $prod){
$items[$prod[‘product_id’]] = $prod[‘name’];
}

$url = ‘https://requestb.in/15k6boy1’;

// do some stuff here

wp_remote_post( $url, array(
‘method’ => ‘POST’,
‘timeout’ => 45,
‘redirection’ => 5,
‘httpversion’ => ‘1.0’,
‘blocking’ => true,
‘headers’ => array(),
‘body’ => array( ‘billingemail’ => $billingEmail, ‘items’ => $items ),
‘cookies’ => array()
)
);
}