在php上为android创建JSON头

我将创建一个用于从数据库接收数据的android应用程序。我测试了我的应用程序，它只能接收特定的JSON格式。我尝试在php文档中添加这个JSON头

header（'Content-Type:application/json；charset=utf-8'）；

然而，它是无用的。

这是我用php:打印的JSON

[
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"s'",'"password'":'"s'"}",
"{'"user'":'"hi'",'"password'":'"tom'"}",
"{'"user'":'"vhj'",'"password'":'"fgg'"}",
"{'"user'":'"d'",'"password'":'"h'"}",
"{'"user'":'"dh'",'"password'":'"hl'"}",
"{'"user'":'"p'",'"password'":'"p'"}",
"{'"user'":'"pon'",'"password'":'"pon'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"s'",'"password'":'"s'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}",
"{'"user'":'"'",'"password'":'"'"}"
] 

我想把它的格式改成这个

{
"goodstart":[
{
    "user": "A",
    "password": "123"
}
]
}

寻求帮助！！！

php代码

<?php
header('Content-Type: application/json');
$con=mysqli_connect(HOST,USER,PASSWORD);
$dbconnect=mysqli_select_db($con, DB) or die ('Select Error:'.mysql_error());
$sql_query="SELECT * FROM `goodstart`"; 
$result=mysqli_query($con, $sql_query);
$output=array();
while($row=$result->fetch_assoc()){
    $output[]= json_encode($row);
}
    print json_encode($output, JSON_PRETTY_PRINT);
mysql_close($con);
?>