PHPがcurl postに基づいてURLを送信するときに中国語が文字化けする場合の対処方法

$url = 'http://'; //调用接口的平台服务地址
$post_string = array('a'=>'b');
$ch = curl_init();
$this_header = array(
"content-type: application/x-www-form-urlencoded;
charset=UTF-8"
);
curl_setopt($ch,CURLOPT_HTTPHEADER,$this_header);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POSTFIELDS, $post_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
curl_setopt($ch, CURLOPT_TIMEOUT, 30);
$result = curl_exec($ch);
if($result)
echo "<script>\nalert(\"同步成功！ \");\n</script>";
curl_close($ch);