$sql="select id,name,superior from table where 1=1";

$requ = mysqli_query($con,$sql);

$items = array();

while($rs=mysqli_fetch_array($requ)){

$a=array("title"=>$rs['name'],"value"=>$rs['id'],"pid"=>$rs['superior']);

array_push($items,$a);

}

$generateTree = function ($items, $parentKey = 'pid') {

    $tree = $temp = array();

    foreach ($items as $item) {

        $temp[$item['value']] = $item;

    }

    foreach ($items as $item) {

        if (isset($temp[$item[$parentKey]])) {

            $temp[$item[$parentKey]]['list'][] = &$temp[$item['value']];

        } else {

            $tree[] = &$temp[$item['value']];

        }

        unset($temp[$item['value']][$parentKey]);

    }

    return $tree;

};

$data = json_encode($generateTree($items));

echo $data;