Export database to json in a specific format - php

Question

When Exporting database to json I get it in this form:
[
{
"id": "1",
"siteId": "1",
"siteUrl": "localhost",
"identity": "mobie",
"lastIp": "127.0.0.1",
"lastLogin": "2018-05-17",
"loginCountry": "GB",
}
]
Warning: Illegal string offset 'id' in C:\xamppp\htdocs\auth\mysql.php on line 81
To all of the $user variables.
My database structure is shown as above in the first json output.
Code
public function db2json($query){
$stmt = $this->db->prepare($query);
$stmt->execute();
$data=$stmt->fetch(PDO::FETCH_ASSOC);
$output = [];
foreach ( $data as $result ) { // Change this to loop over the data
$user = [];
$user["id"] = $result["id"];
$user["siteId"] = $result["siteId"];
$user["lastIp"] = $result["lastIp"];
$user["lastLogin"] = $result["lastLogin"];
$user["loginCountry"] = $result["loginCountry"];
$output[$result["siteUrl"]][$result["identity"]] = $user;
}
echo json_encode($output, JSON_PRETTY_PRINT);
}

Answer 1

I have had to build up some test data, but this will just mean that you change the foreach() to loop over your database result instead. Rather than just assigning the result straight to the output, this just creates the various arrays as you want them in the output...
$output = [];
foreach ( $data as $result ) { // Change this to loop over the data
$user = [];
$user["id"] = $result["id"];
$user["siteId"] = $result["siteId"];
$user["lastIp"] = $result["lastIp"];
$user["lastLogin"] = $result["lastLogin"];
$user["loginCountry"] = $result["loginCountry"];
$output[$result["siteUrl"]][$result["identity"]] = $user;
}
echo json_encode($output, JSON_PRETTY_PRINT);
With my test data, this outputs...
{
"localhost": {
"mobie": {
"id": "1",
"siteId": "1",
"lastIp": "127.0.0.1",
"lastLogin": "2018-05-17",
"loginCountry": "GB"
},
"user2": {
"id": "1",
"siteId": "1",
"lastIp": "127.0.0.1",
"lastLogin": "2018-05-17",
"loginCountry": "GB"
}
},
"othersite": {
"user1": {
"id": "1",
"siteId": "1",
"lastIp": "127.0.0.1",
"lastLogin": "2018-05-17",
"loginCountry": "GB"
}
}
}