Esto te podría valer:
Código PHP:
<?
$host = "your.host.com";
$port = 80;
$postdata = "field1=value1&field2=value2&field3=value3";
if ($sp = fsockopen($host,$port)) {
fputs($sp,"POST /path/to/somescript/php HTTP/1.0 ");
fputs($sp,"Host: $host ");
fputs($sp,"Content-type: application/x-www-form-urlencoded ");
fputs($sp,"Content-length: ".strlen($postdata)." ");
fputs($sp,"Connection: close ");
fputs($sp,$postdata);
// optionally print the response
while (!feof($sp)) {
echo fgets($sp,128);
}
fclose($sp);
} ?>