php - Notice: Trying to get property 'AuthToken' of non-object

one text

I am getting an error while executing code.

Notice: Trying to get property 'AuthToken' of non-object

Anyone please tell me why this error come and what is the solution

here is the code

 $fields = [
        "HS_ChannelId"=>$HS_ChannelId,
        "HS_IsRedirectionRequest"=>$HS_IsRedirectionRequest,
        "HS_MerchantId"=> $HS_MerchantId,
        "HS_StoreId"=> $HS_StoreId,
        "HS_ReturnURL"=> $HS_ReturnURL,
        "HS_MerchantHash"=> $HS_MerchantHash,
        "HS_MerchantUsername"=> $HS_MerchantUsername,
        "HS_MerchantPassword"=> $HS_MerchantPassword,
        "HS_TransactionReferenceNumber"=> $HS_TransactionReferenceNumber,
        "HS_RequestHash"=> $hashRequest
    ];
    
    $fields_string = http_build_query($fields);
    
    //open connection
    $ch = curl_init();
    //set the url, number of POST vars, POST data
    curl_setopt($ch,CURLOPT_URL, $url);
    curl_setopt($ch,CURLOPT_POST, true);
    curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);
    //So that curl_exec returns the contents of the cURL; rather than echoing it
    curl_setopt($ch,CURLOPT_RETURNTRANSFER, true); 
    //execute post
    $result = curl_exec($ch);
    
   $handshake =  json_decode($result);
   
    $AuthToken = $handshake->AuthToken;