使用PHP计算使用Web服务选择distinct

Question

I have a problem with select distinct and calculate my data. I am on restful web service server side. And I made service like this :

private function grafik()
        {
            if($this->get_request_method() !="GET") 
                {
                    $this->response('',406);
                }
                    $sql   = "select distinct operating_system from data";
                    $query = $this->mysqli->query($sql) or die($this->mysqli->error.__LINE__);
                    //$query = mysql_query( $sql )  or die(mysql_error());
                    while( $ret = $query->fetch_array() ){

                    $os=$ret['operating_system'];

                    $sql_jumlah   = "SELECT * FROM data WHERE operating_system='$os'";  
                    $query_jumlah = $this->mysqli->query($sql_jumlah) or die($this->mysqli->error.__LINE__);

                         $data = mysqli_num_rows( $query_jumlah );
                            $jumlah = $mydata;
echo $jumlah;   
echo $os;

The problem is I'm really confused on how I can get $jumlah and $os on different variable into client side with

$json = file_get_contents('http://localhost/proejct/services/server');

When i echo $json, I get both of $jumlah and $os on $json, but I want to get that in 2 different variables. What should I do?