cURL：无法解析主机：xx.com [ping xx.com ok和xx.com是我的本地域名]

function curl_upload($post_url, $post_data) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $post_url);
    curl_setopt($curl, CURLOPT_POST, 1);
    curl_setopt($curl, CURLOPT_POSTFIELDS, $post_data);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($curl, CURLOPT_USERAGENT, "Mozilla/4.0");
    $result = curl_exec($curl);
    $error = curl_error($curl);
    curl_close($curl);
    return $error ? $error : $result;
}

$data = curl_upload('http://xx.com/lists', $condition);
echo $data;exit();

then run the php code ,show me:

sometimes show Could not resolve host: xx.com

sometimes show the right data

i try to solve it，i google it ，but not work. so i ask here for help.

ping xx.com ok

my resolv.conf:

nameserver 8.8.8.8 nameserver 114.114.114.114

myhosts:

/etc/hosts: xx.com 127.0.0.1

who can give me help ,Tks!!