$url = 'https://campaigns.zoho.com/api/v1.1/addlistsubscribersinbulk';

$header = array(
    'Content-Type: application/x-www-form-urlencoded',
    'Authorization: Zoho-oauthtoken '.$access_token,
);

$ch = curl_init($url);
curl_setopt_array($ch, array(
    CURLOPT_POST           => 1,
    CURLOPT_POSTFIELDS     => http_build_query(array(
        'scope' =>'ZohoCampaigns.contact.CREATE',
        'resfmt' => 'json',
        'listkey' => 'listkey',
        'emailids' => $useremail
    )),
    CURLOPT_URL            => $url,
    CURLOPT_HTTPHEADER     => $header,
    CURLOPT_HEADER         => 0,
    CURLOPT_RETURNTRANSFER => TRUE,
    CURLOPT_TIMEOUT        => 30
));

$result = curl_exec($ch);

curl_close($ch);

i am getting error :
({"message":"Unauthorized request.","version":"1","URI":"/api/addlistsubscribersinbulk","Code":"1007","status":"error"})