Flipkart Api：尝试从api检索数据时出错

This is the curl, php program i gave to retrieve data from flip kart using there API. But what ever i do , i am getting the same error as :

{"error":"unauthorized","error_description":"An Authentication object was not found in the SecurityContext"}

<?php

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,"https://api.flipkart.net/oauth-service/oauth/token?grant_type=client_credentials&scope=Seller_Api,Default");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$vars);  //Post Fields
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$headers = array();
$headers[] = 'appid:appsecret';

curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

$server_output = curl_exec ($ch);


print  $server_output ;

curl_close ($ch);

?>

I dont know what is the error , i checked number of time if the problem is with appid and appsecret i gave but still its showing same error.

Flipkart Documentation Link

$action = 'https://sandbox-api.flipkart.net/oauth-service/oauth/token?grant_type=client_credentials&scope=Seller_Api';

$headers = array();
$headers[] = 'content-type: application/json';
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $action);
curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_USERPWD, "<id>:<key>");
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "GET");
curl_setopt($curl, CURLOPT_HEADER, 0);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, true);
$result = curl_exec($curl);
echo '<pre>';print_r($result);
curl_close($curl);