Update wordpress remotely

Hello,
I wanna update wordpress sites from my cpanel.Actually remotely
So, i am making a script :

.........................
//login successful
//upgrading option start
$urlto=('site.com/wp-admin/update-core.php');
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $urlto);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,"upgrade=Update Now");
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_USERAGENT, $useragent);
    curl_setopt($ch, CURLOPT_COOKIEJAR, "COOKIE.txt");
    curl_setopt($ch, CURLOPT_COOKIEFILE, "COOKIE.txt");
$buffer = curl_exec($ch);

I can successfully login remotly from my cpanel by run this script. But it is not upgrading the wordpress.
my wordpress upgrading page html is :

<form method=”post” action=”update-core.php?action=do-core-upgrade” name=”upgrade” class=”upgrade”><input type=”hidden” id=”_wpnonce” name=”_wpnonce” value=”5434b20e73″ /><input type=”hidden” name=”_wp_http_referer” value=”/testser/wp-admin/update-core.php” /><p><input name=”version” value=”3.4.2″ type=”hidden”/><input name=”locale” value=”en_US” type=”hidden”/><input type=”submit” name=”upgrade” id=”upgrade” class=”button-primary” value=”Update Now” /></form>

What is the wrong in this code ?