PHP输出json到web无法正常显示中文

PHP从mysql获取数据后,录入数组并转为json。
最后输出的时候,中文显示为"?"。
这个问题是出在服务器还是php?
在数据库里看,中文是能正常显示的。
PHP代码:

    $result = mysql_query("select * from hpsubject");
    while ($row = mysql_fetch_array($result)) {
        $arr = json_encode(array('hps_userid'=>$row['hps_userid'],
                            $row['hps_userid2'], $row['hps_subid'], $row['hps_type'],
            $row['hps_addr'], $row['hps_distance'], $row['hps_title'], $row['hps_feel'], $row['hps_dowhat'],
            $row['hps_text'], $row['hps_img'], $row['hps_like'], $row['hps_repost'], $row['hps_comment'],
            $row['hps_date'], $row['hps_time'], $row['hps_liveline'], $row['hps_deadline']));
    echo $arr;
    }

输出结果:
{"hps_userid":"1","0":"1","1":"1","2":"????","3":"??","4":"50","5":"??","6":"??","7":"????","8":"??","9":"??","10":"100","11":"100","12":"100","13":"2015-09-21","14":"154436","15":"2015-09-21 15:44:36","16":"2015-09-21 15:44:36"}

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