PHP 发送 json 代码，客户端接收乱码问题

<?php

$db_connect=mysql_connect("localhost","root","root") or die("Unable to connect to the MySQL!");

//选择一个需要操作的数据库
mysql_select_db("emp",$db_connect);
mysql_set_charset('utf8',$db_connect);
//执行 MySQL 语句
$result=mysql_query("SELECT * FROM tianqi");

//提取数据
$row=mysql_fetch_row($result);
$n = 0;
$result = mysql_query("SELECT * FROM tianqi");
while ($row = mysql_fetch_array($result)) {
$arr[$n++] = array(
"id" => $row['id'],
"location" => $row['location'],
"oxygen" => $row['oxygen'],
"negative" => $row['negative'],
"humidity" => $row['humidity'],
"temp" => $row['temp'],
"pm" => $row['pm'],
"createtime" => $row['createtime']
);
}

echo json_encode($arr,JSON_UNESCAPED_UNICODE);

以上代码是我发送给客户端的代码 在网页上打印出来的 json 数据是正确的，但是在客户端接收的数据中，有中文的就变成乱码了