add_action( 'restrict_manage_posts', 'add_export_button' );
function add_export_button() {
    $screen = get_current_screen();

    if (isset($screen->parent_file) && ('edit.php?post_type=certificate' == $screen->parent_file)) {
        ?>
        <input type="submit" name="export_all_posts" id="export_all_posts" class="button button-primary" value="Export All Posts">
        <script type="text/javascript">
            jQuery(function($) {
                $('#export_all_posts').insertAfter('#post-query-submit');
            });
        </script>
        <?php
    }
}

add_action( 'init', 'func_export_all_posts' );
function func_export_all_posts() {
    if(isset($_GET['export_all_posts'])) {
        if(isset($_GET['list'])) {
            $filter = strval($_GET['list']);
        };
        $arg = array(
                'post_type' => 'certificate',
                'post_status' => 'publish',
                'posts_per_page' => -1,
                'tax_query' => array(
                    array(
                        'taxonomy' => 'list',
                        'field'    => 'slug',
                        'terms'    => $filter ,
                    )
                    ),
            );

        global $post;
        $arr_post = get_posts($arg);
        if ($arr_post) {

            header('Content-type: text/csv');
            header('Content-Disposition: attachment; filename="wp.csv"');
            header('Pragma: no-cache');
            header('Expires: 0');

            $file = fopen('php://output', 'w');

            fputcsv($file, array('Post Title', 'URL'));

            foreach ($arr_post as $post) {
                setup_postdata($post);
                fputcsv($file, array(get_the_title(), get_the_permalink()));
            }

            exit();
        }
    }
}