jsonp 返回的是

// Response: jsonp1277656587731([1,2,3,4,5,6,7,8,9])

<?php 
header('content-type: application/json; charset=utf-8');
header("access-control-allow-origin: *");

$cid=$_GET['cid'];

$ch=curl_init('http://m.weather.com.cn/data/'.$cid.'.html');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);//返回字符串，而不是直接输出
$data=curl_exec($ch);
echo $_GET['callback'] . '('.$data.')';
?>

如果需要同时返回 json 和 jsonp 的话

<?php header('content-type: application/json; charset=utf-8');

$data = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
$json = json_encode($data);

echo isset($_GET['callback'])
    ? "{$_GET['callback']}($json)"
    : $json;

via http://www.geekality.net/2010/06/27/php-how-to-easily-provide-json-and-jsonp/