问用PHP提取json字符串

EN

{"accessTokenResponse":{"token":"562371e99fda4296a380547cb5bf9fab","token_type":"Bearer","expires_in_seconds":"77476","client_id":"LTcyMDI1NDI0OQ==","responseStatus":{"code":"100000","message":"Service operation completed successfully","messageDetails":"Access token assigned."}}}

562371e99fda4296a380547cb5bf9fab //-->The Token

<?php
    $user = "LTcyMDI1NDI0OQ==";
    $password = "MjAzMDI5MTU";
    $returnFormat = "json";
    $url = "https://sandbox.dhlecommerce.asia/rest/v1/OAuth/AccessToken?clientId=".$user.
    "&password=".$password."&returnFormat=".$returnFormat."";
    $method = "GET";
    $headers = array(
        "content-type: application/json",
    );

    $curl = curl_init();

    curl_setopt_array($curl, array(
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_URL => $url,
        CURLOPT_CUSTOMREQUEST => $method,
        CURLOPT_HTTPHEADER => $headers,
    ));

    $response = curl_exec($curl);
    $err = curl_error($curl);   

    $result = json_decode($response);

    curl_close($curl);   

    if ($err) {
        echo "cURL Error #:" . $err;
    } else {
        echo $result->token;                
    }
?>

Warning: Undefined property: stdClass::$token in C:\xampp\htdocs\Tracking\getToken.php on line 31