codice:
<form action='/index.php' method='post' enctype="application/x-www-form-urlencoded">
    <input type='text' name='user_name' value='linoma' />
</form>

codice:
        $req = "user_name=linoma";
	$header = "POST /index.php HTTP/1.0\r\n";
	$header .= "Host: www.google.it\r\n";
	$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
	$header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
        fputs($fp,$header . $req);
Credo che 443 sia la porta SSL e la devi indicare nel fsockopen al posto di 80