/**
- @param $url url地址
 - @param $data_string json_encode($arr)
 - @return array
*/ 
function postJson($url, $data_string) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Content-Type: application/json; charset=utf-8',
        'Content-Length: ' . strlen($data_string))
);
ob_start();
curl_exec($ch);
$return_content = ob_get_contents();
ob_end_clean();
$return_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
return array('code'=>$return_code, 'result'=>$return_content);}