Filter WordPress posts by custom taxonomy term with AJAX

ajax-get-posts.php

<?php
function vb_filter_posts() {

    if( !isset( $_POST['nonce'] ) || !wp_verify_nonce( $_POST['nonce'], 'bobz' ) )
        die('Permission denied');

    /**
     * Default response
     */
    $response = [
        'status'  => 500,
        'message' => 'Something is wrong, please try again later ...',
        'content' => false,
        'found'   => 0
    ];

    $tax  = sanitize_text_field($_POST['params']['tax']);
    $term = sanitize_text_field($_POST['params']['term']);
    $page = intval($_POST['params']['page']);
    $qty  = intval($_POST['params']['qty']);

    /**
     * Check if term exists
     */
    if (!term_exists( $term, $tax) && $term != 'all-terms') :
        $response = [
            'status'  => 501,
            'message' => 'Term doesn\'t exist',
            'content' => 0
        ];

        die(json_encode($response));
    endif;

    /**
     * Tax query
     */
    if ($term == 'all-terms') : 

        $tax_qry[] = [
            'taxonomy' => $tax,
            'field'    => 'slug',
            'terms'    => $term,
            'operator' => 'NOT IN'
        ];
    else :

        $tax_qry[] = [
            'taxonomy' => $tax,
            'field'    => 'slug',
            'terms'    => $term,
        ];
    endif;

    /**
     * Setup query
     */
    $args = [
        'paged'          => $page,
        'post_type'      => 'post',
        'post_status'    => 'publish',
        'posts_per_page' => $qty,
        'tax_query'      => $tax_qry
    ];

    $qry = new WP_Query($args);

    ob_start();
        if ($qry->have_posts()) :
            while ($qry->have_posts()) : $qry->the_post(); ?>

                <article class="loop-item">
                    <header>
                        <h2 class="entry-title"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
                    </header>
                    <div class="entry-summary">
                        <?php the_excerpt(); ?>
                    </div>
                </article>

            <?php endwhile;

            /**
             * Pagination
             */
            vb_ajax_pager($qry,$page);

            $response = [
                'status'=> 200,
                'found' => $qry->found_posts
            ];

            
        else :

            $response = [
                'status'  => 201,
                'message' => 'No posts found'
            ];

        endif;

    $response['content'] = ob_get_clean();

    die(json_encode($response));

}
add_action('wp_ajax_do_filter_posts', 'vb_filter_posts');
add_action('wp_ajax_nopriv_do_filter_posts', 'vb_filter_posts');