Just been doing that myself today... here is code I have working for me...
$data = array("a" => $a);
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "PUT");
curl_setopt($ch, CURLOPT_POSTFIELDS,http_build_query($data));
$response = curl_exec($ch);
if (!$response)
{
return false;
}
src: http://www.lornajane.net/posts/2009/putting-data-fields-with-php-curl