redirect php con passaggio post dei parametri

[speriamobene]

bene.
allora ho scritto:

function sendToHost($host,$method,$path,$data,$useragent=0)
{
    $buf = '';
    // Supply a default method of GET if the one passed was empty
    if (empty($method)) {
        $method = 'GET';
    }
    $method = strtoupper($method);
    
    $fp = fsockopen ($host, 80, $errno, $errstr, 30);
    if (!$fp) {
        $buf.= "$errstr ($errno)
\n";
    } else {
   
        if ($method == 'GET') {
            $path .= '?' . $data;
        }
        fputs($fp, "$method $path HTTP/1.1\r\n");
        fputs($fp, "Host: $host\r\n");
        fputs($fp,"Content-type: application/x-www-form- urlencoded\r\n");
        fputs($fp, "Content-length: " . strlen($data) . "\r\n");
        if ($useragent) {
            fputs($fp, "User-Agent: MSIE\r\n");
        }
        fputs($fp, "Connection: close\r\n\r\n");
        if ($method == 'POST') {
            fputs($fp, $data);
        }
    
        while (!feof($fp)) {
            $buf .= fgets($fp,128);
        }
        fclose($fp);
    }
    return $buf;
} 

passando per 'POST' e dove $data è:

$data = "Content-Disposition: form-data; name=\"".'pippo'."\"\r\n";
$data .= "\r\n".'valorepippo'."\r\n";

ma ottengo errore 400 Bad Request !!

come mai?