Wordpress：主导航数组中的循环字段

I'm working on a WP-site with a custom Nav-menu. Each page has ACF-fields repeater fields. I wish to make a scroll-to-sub-menu with by echoing a loop of all the fields of a specific page. If I put the loop inside the $mainNav array, I get a php error. I tried to start the loop before the array, and end it after, but that just prints 1 (the last) info_block_header. Glad for any help :)

sidebar.php:

<nav id="mainNav">

            <?php 
                $mainNav = array(
               'theme_location'  => '',
               'menu'            => 'main-menu', 
               'container'       => 'ul', 
               'container_class' => 'topmenu-{topmenu slug}-container', 
               'container_id'    => 'topmenu',
               'menu_class'      => 'topmenu', 
               'menu_id'         => 'topmenu-{topmenu slug}[-{increment}]',
               'echo'            => true,
               'fallback_cb'     => 'wp_page_menu',
               'before'          => '',
               'after'           => '<ul id="about" class="dropDown">
                                        '. if(get_field('info_block')):
                                        while(has_sub_field('info_block')): .'
                                        <li><a href="#">'. get_sub_field('info_block_header') .'</a></li>'
                                        . endwhile; endif; .'
                                    </ul>',
               'link_before'     => '<h4>',
               'link_after'      => '</h4>',
               'items_wrap'      => '<ul id="%1$s" class="%2$s">%3$s</ul>',
               'depth'           => 0,
               'walker'          => ''
              );

            wp_nav_menu( $mainNav ); 

            ?>

                <?php get_search_form(); ?>
    </nav>