How to get HTML of a sidebar content in wordpress?

Question

I can get a list of sidebars by going through wp_registered_sidebars

<?php foreach ( $GLOBALS['wp_registered_sidebars'] as $sidebar ) { ?>
     <input value="<?php echo ucwords( $sidebar['id'] ); ?>">
              <?php echo ucwords( $sidebar['name'] ); ?>
<?php } ?>

And I can output the sidebar with

<?php echo dynamic_sidebar( ucwords( $sidebar['id'] )); ?>

But I need to output the HTML content out.

I am trying to insert the sidebar in a menu (megamenu), and I am following this post on how to get the metabox appear in my Menus page. I've done it all, I can get the name, id of the sidebar, everything. It's just when I try to add HTML content in my description field of the menu, I don't know how. If I put the dynamic_sidebar I'll get the actuall sidebar in my menus page, and that's not what I want.

So any help is appreciated.

Is it possible to do it with ob_start() function?

EDIT

I tried with:

<?php
    ob_start();
    dynamic_sidebar($sidebar['id']);
    $sidebar_html = ob_get_contents();
    ob_end_clean();
?>

But when I echo that variable inside the hidden input field

<input type="hidden" class="menu-item-description" name="menu-item[-1][menu-item-description]" value="<?php echo $sidebar_html; ?>">

I still get the html out. I just need it as a text html that won't be 'executed'.

Answer 1

Ok, htmlentities() did it

<input type="hidden" class="menu-item-description" name="menu-item[-1][menu-item-description]" value="<?php echo htmlentities($sidebar_html); ?>">