Update capped amount of recurring charge using REST API

[user072319]

Hi there, 

I am trying to update the capped amount of recurring charge using Shopify REST API. I'm using the below PHP code to update the charge.

$recurringChargeShopifyAPIURL = "https://xxxxxxxxxx.myshopify.com/admin/api/2022-01/recurring_application_charges/xxxxxxxxxx/customize.json?recurring_application_charge[capped_amount]=49.99";

$recurringChargeArray = array();
$recurringChargeArray["recurring_application_charge"] = array("capped_amount" => 49.99);

.......

// curl to update the capped amount

.........

The cURL response is NULL. 

Can anyone help what I am doing wrong?

Thanks in advance.