API. Method 'host.create'. Error 'Invalid Request.'

[stincv]

Hi.

The script looks like this:

$url = "http://***/zabbix/api_jsonrpc.php";

function send_request($url,$json) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
    curl_setopt($ch, CURLOPT_URL,$url);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS,$json);
    curl_setopt($ch, CURLOPT_USERPWD, "***:***");
    $result=curl_exec($ch);
    curl_close($ch);
    return json_decode($result);
}

$json = '{
   "jsonrpc": "2.0",
   "method": "user.login",
   "params": {
      "user": "admin",
      "password": "***"
   },
   "id":1
}';

$res = send_request($url,$json);
$auth = $res->result;
var_dump($auth);

$json = '{
    "jsonrpc": "2.0",
    "method": "host.create",
    "params": {
        "host": "domain.ru",
        "interfaces": [
            {
                "type": 1,
                "main": 1,
                "useip": 1,
                "ip": "192.168.0.1",
                "dns": "domain.ru",
                "port": "10050"
            }
        ],
        "groups": [
            {
                "groupid": "9"
            }
        ],
        "templates": [
            {
                "templateid": "10130"
            }
        ],
    },
    "auth": "'.$auth.'",
    "id":1
}';

$res = send_request($url,$json);
var_dump($res); 

The output is:

string(32) "c96ceaf1051c3410a43f73541f8c1c05"                                                                                                                                           
object(stdClass)#2 (3) {                                                                                                                                                                
  ["jsonrpc"]=>                                                                                                                                                                         
  string(3) "2.0"                                                                                                                                                                       
  ["error"]=>                                                                                                                                                                           
  object(stdClass)#3 (3) {                                                                                                                                                              
    ["code"]=>                                                                                                                                                                                              
    int(-32600)                                                                                                                                                                                             
    ["message"]=>                                                                                                                                                                                           
    string(16) "Invalid Request."                                                                                                                                                                                                     
    ["data"]=>                                                                                                                                                                                                                        
    string(34) "JSON-rpc version is not specified."                                                                                                                                                                                   
  }                                                                                                                                                                                                                                   
  ["id"]=>                                                                                                                                                                                                                                                            
  NULL                                                                                                                                                                                                                                                                
} 

As can be seen the first authorization request passes but the second request "----" does not pass, although the request was for the documents and errors there may be no.
Help, why the error?

==============================
I found a solution to the problem itself
after the last element of the array must not be a comma