PHP cURL如何发送JSON Body作为POST请求参数？

<?php$curl = curl_init();curl_setopt_array($curl, array(  CURLOPT_URL => 'http://localhost/xxx',  CURLOPT_RETURNTRANSFER => true,  CURLOPT_ENCODING => '',  CURLOPT_MAXREDIRS => 10,  CURLOPT_TIMEOUT => 0,  CURLOPT_FOLLOWLOCATION => true,  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,  CURLOPT_CUSTOMREQUEST => 'POST',  CURLOPT_POSTFIELDS =>'{    "appid": "111",    "secret": "ddd111",    "an": "xxx"}',  CURLOPT_HTTPHEADER => array(    'Content-Type: application/json',    'Cookie: lang=zh-cn; ssid=02bebb340032d3a9e4b15463dd7d0eaa'  ),));$response = curl_exec($curl);curl_close($curl);echo $response;