phpポストjsonデータ

function http_post_data($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($return_code, $return_content);
}
 $url = "http://www.xxxx.com";
 $data = json_encode(array('cmd'=>"Query_Ranking_Sys",'group'=>1,'room'=>0,'name'=>"RoomSvr",'value'=> array(0=>array('key'=>5,'beginindex'=>0,'count'=>10))));
 list($return_code, $return_content) = http_post_data($url, $data);

php、ポスト、json