Get external HTML code Render

I am putting together a PDF and in this PDF I have to put a graph that is being done by Highcharts . I created an HTML and JS code, and it is creating the right one, the problem is that I need to get the HTML code of this rendered graphic and when I make the request in the link of the page that mounts the graphic, it brings the HTML not rendered, that is , without running JS to mount the chart.

<?php

public function SendRequest($url){

        $curl_handle=curl_init();
        curl_setopt($curl_handle, CURLOPT_URL, $url);
        curl_setopt($curl_handle, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($curl_handle, CURLOPT_FOLLOWLOCATION, 1);
        $query = curl_exec($curl_handle);
        curl_close($curl_handle);

        return $query;
}

public function cria_grafico($id_pedido, $id_produto){

     echo $this->load->view('sellins/GeraGraficoSellinB4', array('id_pedido'=>$id_pedido, 'id_produto'=>$id_produto), TRUE);

}

public function download($codigo_pedido = false){

$grafico = $this->SendRequest(base_url('Sellin_B4/cria_grafico/'.$produto['idPedido'].'/'.$produto['codigoProduto']));

$file = 'uploads/extract_sellin_goagro_'.time().'.pdf';

$mpdf = new mPDF();

$mpdf->SetHeader('Go Agro - Extract Sellin');

$mpdf->writeHTML($grafico);

$mpdf->SetFooter('{PAGENO}');

$mpdf->Output($file, 'F');

}

In the create_graphic method this is where it calls HTML with JS and mounts the chart. If I access the link miite.com.br/cria_grafico it shows the graphic rendered, but when I make a request to obtain the same result via code, it brings HTML without being rendered.