function postUrl($url, $postvar)
{
    $ch = curl_init();
    $headers = array(
        "POST".$url."HTTP/1.0",
        "Content-type: text/xml; charset=\"gb2312\"",
        "Accept: text/xml",
        "Content-length: ".strlen($postvar)
    );
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postvar);
    $res = curl_exec ($ch);
    curl_close ($ch);
    return $res;
}

$baiduXML = "<?xml version=\"1.0\" encoding=\"gb2312\"?>
<methodCall>
  <methodName>weblogUpdates.extendedPing</methodName>
  <params>
    <param><value><string>愚人渡</string></value></param>
    <param><value><string>//www.jb51.net</string></value></param>
    <param><value><string>//www.jb51.net/read.php?tid-96.html</string></value></param>
    <param><value><string>//www.jb51.net</string></value></param>
  </params>
</methodCall>";

$res = postUrl('http://ping.baidu.com/ping/RPC2', $baiduXML);

if ( strpos($res, "<int>0</int>") )
{
    echo "PING成功";
}else{
    echo "PING失败";
}