Cookie file not being written to php curl - php

Question

I recently installed a LAMP stack on an Ubuntu server. I am having problems with my curl script. I have the following code:
function curl_request($page, $postvalues = false) {
$ch = curl_init();
// curl_setopt($ch, CURLOPT_NOBODY, false);
curl_setopt($ch, CURLOPT_COOKIEJAR, "/var/www/html/cookie.txt");
curl_setopt($ch, CURLOPT_COOKIEFILE, "/var/www/html/cookie.txt");
if (isset($postvalues) && $postvalues != false) {
curl_setopt($ch, CURLOPT_POSTFIELDS, $postvalues);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POST, 1);
}
curl_setopt($ch, CURLOPT_URL, $page);
curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7");
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($ch, CURLOPT_VERBOSE, 1);
$result = curl_exec($ch);
echo "CURL ERROR<BR />" . curl_error($ch) . "<br /><br /><br />";
curl_close($ch);
return $result;
}
Whenever I run this script, it never edits the /var/www/html/cookie.txt file.
The file is always blank. I've changed the permissions and done all of that, changed the file name, tried using relative path, etc. Why is the file not being edited?