使用PHP将另一个数据添加到json数组

I'm trying to create a JSON array with loop, I stored languages name in database and retrieving from query, after that I need to convert it into this format

$arrayName = array('lang-1' => null , 'lang-2' => null, ..... ,'lang-n' => null );

how can I achieve that

PHP code is like this

include_once "inc/init.php";
header('Content-Type: application/json');
$arrayName = array();
$query = $db->query("SELECT * FROM `medium`");
while ($data = mysqli_fetch_assoc($query)) {
array_push($arrayName, $data['medium']);
}
echo json_encode($arrayName);

im getting in this format

[
 "Kannada",
 "Telugu",
 "Tamil",
 "Urdu",
 "Spanish",
 "Arabian"
]

im trying pushing value but im not getting in that format, please help me

Thank you

Based on your comments I'm asuming that $data['language'] represents a name of your language. Then you can achieve your goal by the following code:

include_once "inc/init.php";
header('Content-Type: application/json');
$arrayName = array();
$query = $db->query("SELECT * FROM `medium`");

while ($data = mysqli_fetch_assoc($query)) {
    $arrayName[$data['language']] = null; // $array[$key] = $value
}

echo json_encode($arrayName);

using array_push you will get the same result

include_once "inc/init.php";
header('Content-Type: application/json');
$arrayName = array();
$query = $conn->query("SELECT * FROM `medium`");
while ($data = mysqli_fetch_assoc($query)) {
array_push($arrayName,$data['language ']);

}
$arrayName=array_fill_keys($arrayName, 'null'); 
echo json_encode($arrayName);