Converting list of values from MySQL into array with square brackets

I want to display a chart with ApexCharts from MySQL data.

I am connecting to my database via axios and a php-file with functions that communicate with the database. A typical vue method looks like:

myfunction: function(){
  axios.post('ajaxfile.php', {
    request: 1,
  })
  .then(function (response) {
    alert(response.data);
  })
  .catch(function (error) {
    console.log(error);
  });
  },

In ajaxfile.php this request is being continued like this and echoed back as json encoded:

if($request == 1){
$data = mysqli_query($con,"SELECT * from mytable");

  $result = array();
  while($row = mysqli_fetch_assoc($data)){
    $result[]=$row;
  }
  echo json_encode($result);
  exit;
}

ApexCharts pulls data in the data section of vue.js like this, which (in this case) is the base for a pie chart with 30% and 70% data:

data: {
    chartdata: [30, 70],
}

What I’d like to achieve is selecting two numeric values from my database in my ajaxfile.php and create a pie chart from it. So something like:

if($request == 1){
$data1 = mysqli_query($con,"SELECT * from mytable WHERE id=1");
  $result1 = mysqli_fetch_assoc($data1);

$data2 = mysqli_query($con,"SELECT * from mytable WHERE id=2");
  $result2 = mysqli_fetch_assoc($data2);

 $chartdata = $result1.','.$result2;

  echo json_encode($chartdata);
  exit;
}

And in Vue.js:

  myfunction: function(){
      axios.post('ajaxfile.php', {
        request: 1,
      })
      .then(function (response) {
        app.chartdata = response.data;
      })
      .catch(function (error) {
        console.log(error);
      });
      },

The chartdata from my ajaxfile should then be saved in app.chartdata in vue, so that ApexCharts can build the chart from it.

But how can I achieve the needed format?

[30,70]

I pretty much tried everything. Even rebuilding the format with additional brackets didn't help. Like:

app.chartdata ="[ "+app.chartdata +" ]";