plugin.php

add_action('save_post', 'purge_cache');

function purge_cache($post_ID)
{
            $url =  get_permalink($post_ID, true);
                echo ping_cloudflare($url);}

function ping_cloudflare($url)
{
            $body = array();
                $body['files'] = [$url];

                $api_key = 'key';
                    $email = '[email protected]';
                    $zone_id = 'id';
                        $endpoint = "https://api.cloudflare.com/client/v4/zones/$zone_id/purge_cache";
                        $http_settings = array(
                                        'method'=>'POST',
     'headers'=>array(
           'Content-Type'=>'application/json',
               'X-Auth-Email'=>$email,
           'X-Auth-Key'=>$api_key,
           ),
       'body'=>json_encode($body),
       'data_format'=>'body'
   );
                            $response = wp_remote_request($endpoint, $http_settings);
                            $response_body = wp_remote_retrieve_body($response);
                                $result = json_decode($response_body);

                                if ($result->success == true) {
     echo "Cache PURGED";
   }else{
   echo "Purge FAILED";
   }
}