$tmp = [];
            $tmp['id'] = 'aaa';
            $tmp['name'] = 'bbb';
            $tmp['vvvv'] = [
                'www'=>1,
                'ffff'=>2
            ];
            
            echo (json_encode($tmp));

The output is

{
"id": "aaa",
"name": "bbb",
"vvvv": {
    "www": 1,
    "ffff": 2
}
}

I would like to ask how to change the output to

{
"id": "aaa",
"name": "bbb",
"vvvv": [
    {"www": 1},
    {"ffff": 2}
]
}

I have tested that this works, but it is not very easy to use:

    $tmp['vvvv'] = [
                0=>(object)['www'=>1],
                1=>(object)['fff'=>2]
            ];