Formatting Query into Json for AJAX call

Hey all, looking to have a nested loop feed data into a json-able php array, encode that array, then be able to call it via AJAX. I have the AJAX part down, but making the array properly is giving me some trouble.

Code for what the JSON should look like (rough outline):

[{
    "topic-title" : [
         {
              "title" : "the_title",
              "link" : "get_permalink"
         },{
              "title" : "the_title",
              "link" : "get_permalink"
         }
         // etc.
    ] ,
    "next-topic-title : [
         {
              "title" : "the_title",
              "link" : get_permalink"
         }, {
              "title" : "the_title",
              "link" : "get_permalink"
         }
         // etc.
    ]
    // etc.
}]

It should be echoed from this code, but I’m getting ‘undefined’ when I console.log it in the browser.

function reload_topics() {
        $final = array();
        $tax_sh = get_terms(
            array(
                'section'
            ),array(
                'orderby' => 'name',
                'order' => 'ASC',
                'hide_empty' => true,
                'hierarchical' => true
            )
        );
        foreach ($tax_sh as $term) {
            $argsh = array(
                'post-type' => 'custom-post-type',
                'tax_query' => array(
                    array(
                        'taxonomy' => 'section',
                        'field' => 'slug',
                        'terms' => $term->slug
                    )
                )
            );
            $content = array();
            $this_term = $term->slug;
            $content[$this_term] = array();
            $inner_query = new WP_Query($argsh);
            if( $inner_query -> have_posts() ) : while( $inner_query -> have_posts() ) : $inner_query->the_post();
                $this_post = array("title" => get_the_title(), "link" => get_permalink($post->ID));
                array_push($content[$the_term],$this_post);
            endwhile;
            else:
            endif;
            array_push($final,$content);
        }
        $final_encode = json_encode($final);
        echo $final_encode;
        die();
    }

If there is a much easier way to do this or a tutorial I can work through that would be much appreciated, but I haven’t been able to enter the correct terms into Google to find a good tutorial, except the upvote downvote tutorial that is on a few sites; it does not cover this exactly, but definitely helped with the AJAX part.

Thanks!