How to call wp-mpdf from php? With `mpdf_exec()`?

Hi all,

I was wondering if you can call wp-mpdf from php?
I thought on making a ajax callback function to select a (custom)template .

Is this possible? maybe with mpdf_exec() or mpdf_output()?
mpdf_output() looks most promising, since you can set the template path. If you can do this you don’t have to change the DB option setting mpdf_theme.

My first approach works. But it’s ugly: It sets a new value in the DB and then runs the url to get the pdf.

JS:

    <script type="text/javascript">
        jQuery(document).ready(function ($) {

            $(".button-pdf-1").click(function (e) {
                e.preventDefault();

                var data = {
                    'action': 'my_action',
                    'post_id': <?php echo get_the_ID(); ?>,
                    'template': 'rtt_pdf_01'
                };

                getPdf(data);

            });

            $(".button-pdf-2").click(function (e) {
                e.preventDefault();

                var data = {
                    'action': 'my_action',
                    'post_id': <?php echo get_the_ID(); ?>,
                    'template': 'rtt_pdf_02'
                };

                getPdf(data);

            });

            function getPdf(data) {
                jQuery.post(ajaxurl, data, function (response) {

                    let url = '<?php echo get_post_permalink( get_the_ID()); ?>?output=pdf';
                    window.location.href = url;
                });
            }

        });
    </script>

php:

    add_action('wp_ajax_my_action', 'my_action');
    
    function my_action()
    {
        update_option('mpdf_theme', $_POST['template']);
        die();
    }

——————-

Second approach should be less hacky. But I don’t get it to work. This is the current code:
JS:

    <script type="text/javascript">
        jQuery(document).ready(function ($) {

            $(".button-pdf-1").click(function (e) {
                e.preventDefault();

                var data = {
                    'action': 'my_action',
                    'post_id': <?php echo get_the_ID(); ?>,
                    'template': 'rtt_pdf_01'
                };

                getPdf(data);

            });

            $(".button-pdf-2").click(function (e) {
                e.preventDefault();

                var data = {
                    'action': 'my_action',
                    'post_id': <?php echo get_the_ID(); ?>,
                    'template': 'rtt_pdf_02'
                };

                getPdf(data);

            });

            function getPdf(data){
                jQuery.post(ajaxurl, data, function (response) {

                    // Should I need this? Plus is this the best way?
                    var blob = new Blob([response]);
                    var link = document.createElement('a');
                    link.href = window.URL.createObjectURL(blob);
                    link.download = "FILENAME_TO_SAVE_WITH_EXTENSION.pdf";
                    link.click();

                });
            }

        });
    </script>

php callback:

    add_action('wp_ajax_my_action', 'my_action');

    function my_action()
    {
        global $post, $_GET;

        // should I require this? Plus is there an easier way to get the path?
        require_once( rtt_get_current_file_path(__DIR__) ."/../../../../plugins/wp-mpdf/wp-mpdf.php");

        //catch current theme to reset it later
        $currentPdfTheme = get_option('mpdf_theme');

        // set it, since <code>mpdf_exec()</code> looks for it.
        $_GET['output'] = 'pdf';

        // set the desired template
        update_option('mpdf_theme', $_POST['template']);

        // to-do, somehow it fetches the first post instead of $_POST['post_id'] value
        $arg = array(
            'include' => [$_POST['post_id']],
        );
        $posts = get_posts( $arg );

        foreach ( $posts as $post ) {

            query_posts( 'p=' . $_POST['post_id'] );

            // Approach 1
            //mpdf_exec( 'false' );

            // Approach 2
            $pdf_output = '';
            $outputToBrowser = true;
            $pdfName = 'Export_' . get_the_title(); //could also get slug
            $templatePath = ''; // ? Do I need to set this? Also, I can maybe use this so I dont have to change DB option <code>mpdf_theme</code>?
            mpdf_output( $pdf_output, true, $outputToBrowser, $pdfName, $templatePath );
        }

        //reset original theme
        update_option('mpdf_theme', $currentPdfTheme);

        die();
    }

Am I on the right track here? How can I successfully get the pdf with php and return/download it client side?