API アクセス時の 401 Unauthorized エラーを回避するために Curl セッションを維持するにはどうすればよいですか?

define("COOKIE_FILE", "cookie.txt");

// Login the user
$ch = curl_init('http://api.example.com/login/joe/smith');
curl_setopt ($ch, CURLOPT_COOKIEJAR, COOKIE_FILE); 
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);
echo curl_exec ($ch);

// Read the session saved in the cookie file
echo "<br /><br />";
$file = fopen("cookie.txt", 'r');
echo fread($file, 100000000);   
echo "<br /><br />";

// Get the users details
$ch = curl_init('http://api.example.com/user');
curl_setopt ($ch, CURLOPT_COOKIEJAR, COOKIE_FILE); 
**curl_setopt ($ch, CURLOPT_COOKIEFILE, COOKIE_FILE);** // **Set the cookie file** 
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);
echo curl_exec ($ch);