You'll find php/curl examples here: http://curl.haxx.se/libcurl/php/examples/, especially http://curl.haxx.se/libcurl/php/examples/simplepost.html
<?php
//
// A very simple PHP example that sends a HTTP POST to a remote site
//
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,"http://www.mysite.com/tester.phtml");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS,
"postvar1=value1&postvar2=value2&postvar3=value3");
// in real life you should use something like:
// curl_setopt($ch, CURLOPT_POSTFIELDS,
// http_build_query(array('postvar1' => 'value1')));
// receive server response ...
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$server_output = curl_exec ($ch);
curl_close ($ch);
// further processing ....
if ($server_output == "OK") { ... } else { ... }
?>