Código PHP para trackbacks simples

<?php


	function _sendPingBack($from,$to,$pingback){
		
		$xml = '<?xml version="1.0"?><methodCall><methodName>pingback.ping</methodName><params>'.
               '<param><value><string>'.$from.'</string></value></param>'.
                '<param><value><string>'.$to.'</string></value></param>'.
                '</params></methodCall>';
				
        				
        $rq = curl_init();
        curl_setopt($rq, CURLOPT_URL, $pingback);
        curl_setopt($rq, CURLOPT_POST, 1);
        curl_setopt($rq, CURLOPT_POSTFIELDS, $xml);
        $algo=@curl_exec($rq);
        curl_close($rq);
		
	}
?>