How to get the filename of exported image of FusionChart in Server-Side?

[How to get the filename of exported image of FusionChart in Server-Side?]

I'm using following FusionChart option to Save the image to Server-Side

PHP:

  [ 'chart' => [
      "exportEnabled" => "1",
      "exportAtClient" => "0",
      "exportAction" => "save",
      "exportHandler" => "/fusioncharts/export-handlers/php-export-handler/index.php",
      "exportFileName" => $chartImagesFileName,
    'categories' => [ ['category' => $labels] ],
    'dataset' => [
      ['seriesname' => '...', 'data' => $reg],
      ['seriesname' => '...', 'data' => $billed]
    ]
  ]

Javascript:

$(document).on('click', '#download-csv', function(e) {
        var id = "#" + chartUid + " .fusioncharts-container div:contains('Export As PNG')" ;
        $( id ).trigger("click");
});

Here, /fusioncharts/export-handlers/php-export-handler/index.php is able to generate image and print the filename.

But my problem is, on triggering click, I'm unable to get the filename.

How can I resolve this issue in FusionChart?