$url = $file_name;
//The data you want to send via POST
$fields = [
'__VIEWSTATE ' => $state,
'__EVENTVALIDATION' => $valid,
'btnSubmit' => 'Submit'
];
//url-ify the data for the POST
$fields_string = http_build_query($fields);
//open connection
$ch = curl_init();
//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL, $url);
curl_setopt($ch,CURLOPT_POST, count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);
//So that curl_exec returns the contents of the cURL; rather than echoing it
curl_setopt($ch,CURLOPT_RETURNTRANSFER, true);
//execute post
$result = curl_exec($ch);
echo $result;