How to export to csv file a PHP Array with a button?

Question

I have 3 charts on my page, they are made from 3 PHP arrays. I would like to print the data from these arrays by clicking a button below each chart. I could do all the queries again in the file which will print the csv file, but I guess it would be unnecessary to have such repeated code this way.

I tried putting the arrays data on hidden inputs, converting them with json_encode first, and then in JS by clicking these buttons will get it and send it through ajax to the file which will convert it again to a PHP object with json_decode and then make the csv to print it. Well it didn't work and I don't know why. Here's the relevant code:

...
<canvas id="1" width='60%' height='15%'></canvas>
<input type="hidden" id="dataCanvas1" value="<?=htmlspecialchars(json_encode($valores1, JSON_UNESCAPED_SLASHES))?>">
<button type="button" class="btn btn-info" onclick="bajarCSV('dataCanvas1')">Bajar CSV</button>
...
<script>
function bajarCSV(id){
        var array = $("#"+id).val();
        $.ajax({
          data: {
            "array": array
          },
          dataType:"json",
          url:  "acciones/bajarCSV.php",
          type:  'post'
        });
      }
    </script>

Here's the "bajarCSV.php" code:

$array = json_decode($_REQUEST['array'], TRUE);

header("Content-Disposition: attachment;filename=data.csv");
header("Content-Transfer-Encoding: binary");

ob_start();
$output = fopen('php://output', 'w');
fputcsv($output, array('Fecha','Valor'));

// loop over the rows, outputting them
foreach($array as $element) {
  fputcsv($output, $element);
}

fclose($output);
return ob_get_clean();

And here's an example of how the resultant array is formed on "bajarCSV.php"

array (size=184)
  0 => 
    array (size=2)
      'x' => string '2019-10-02 11:30:00' (length=19)
      'y' => int 9266
  1 => 
    array (size=2)
      'x' => string '2019-10-02 11:33:00' (length=19)
      'y' => int 7831
  2 => 
    array (size=2)
      'x' => string '2019-10-02 11:36:00' (length=19)
      'y' => int 7649
  3 => 
    array (size=2)
      'x' => string '2019-10-02 12:57:00' (length=19)
      'y' => int 8509
  4 => 
    array (size=2)
      'x' => string '2019-10-02 13:00:00' (length=19)
      'y' => int 8815
  5 => 
    array (size=2)
      'x' => string '2019-10-02 13:03:00' (length=19)
      'y' => int 8666
  6 => 
    array (size=2)
      'x' => string '2019-10-02 11:42:00' (length=19)
      'y' => int 9064
  7 => 
    array (size=2)
      'x' => string '2019-10-02 11:45:00' (length=19)
      'y' => int 9013
...

The problem is, basically, when I click the button, the AJAX would execute but nothing is returned from it, nor a error nor the csv printed nor the download.

I hope that all this it's well explained, thanks.

UPDATE 1

Tried the fetch approach, but I can't/don't know how send my JSON array to the page, to form by it the csv file, so the csv resultant now it's filled with html code of the error page.