nodejs 回调问题

为何下面的

``
module.exports.fans = function(callback) {
var selectSQL = "SELECT * FROM `fans` WHERE `statu`= 0";
connection.query(selectSQL,function(err, rows) {
if (err) throw err;
var op = {};
var cookie ='';
for(var id in rows){
/*superagent.get('http://gxwx.xmtsw.com/wechat/page/index/title/?openid='+rows[id].openid)
.end(function(err,res){
cookie = res.header['set-cookie'].join(',').match(/(PHPSESSID=.+?);/)[1];
//op[rows[id].wxid]=rows[id].openid;
});*/
op[rows[id].wxid]=rows[id].openid;
//callback(op);
}
callback(op);
});
connection.end();
}``


superagent 外面的 callback 里能正常返回
``{ xudada0509: 'oVFWVjm***VDtygxoUta0',
xuchangyu77: 'oVFWVjrgX***3PKET83almQoz2gw',
linchunhua77: 'oVFWVjhLYe***K0UA1PGmp4N0flI',
linchunhua55: 'oVFWVjjGopj***UStfHc2JqyDwCA',
pangwanglin: 'oVFWVjkCg***_wxQ2bmhu2UkIxro' }``

放 superagent 里面就是没都没有？

求解