How to call code when adding WooCommerce menu items via woocommerce_account_menu_items

Question

I'm inserting menu items similar to the code example at https://wordpress.stackexchange.com/a/277080/137417, but I haven't encountered endpoints before and the documentation and tutorial I've looked at seem a bit beyond... Presumably, there must be a way to specify a function or something to generate the output? Or somewhere to hook into. (Or does it have to be via a template file in the theme?)

I thought maybe i should create it as a query var:

add_filter('query_vars', 'add_query_vars');
function add_query_vars($vars) {
    $vars[] = "2nd-item";
    return $vars;
}

but I'm still staring at a good old error404 when i click the link and call

...://site.com/shop/my-account/2nd-item/

Any direction much appreciated, t.i.a.

Answer 1

One needs to create an action hook 'woocommerce_account_[myendpoint]_endpoint':

add_action('woocommerce_account_' . $endpoint . '_endpoint', 'my_endpoint_content');

function my_endpoint_content() {
    //content goes here
    echo 'My content goes here';
}

http://hookr.io/actions/woocommerce_account_key_endpoint/

So, putting a few different sources together, to add a new menu item to the Woocommerce My Account dashboard one needs something like:

    <?php

add_filter('woocommerce_account_menu_items', 'add_my_menu_items');

function add_my_menu_items($items) {
    $my_items = array('2nd-item' => __('2nd Item', '[my_plugin]'),);
    $my_items = array_slice($items, 0, 1, true) +
            $my_items +
            array_slice($items, 1, count($items), true);
    return $my_items;
}

//so, for...
$endpoint = '2nd-item';

add_action('init', 'my_custom_endpoint');

function my_custom_endpoint() {
    add_rewrite_endpoint('2nd-item', EP_ROOT | EP_PAGES);
}

add_action('woocommerce_account_' . $endpoint . '_endpoint', 'my_endpoint_content');

function my_endpoint_content() {
    //content goes here
    echo 'My content goes here';
}

add_filter('query_vars', 'my_custom_query_vars', 0);

function my_custom_query_vars($vars) {
    $vars[] = '2nd-item';
    return $vars;
}

add_action('wp_loaded', 'my_custom_flush_rewrite_rules');

function my_custom_flush_rewrite_rules() {
    flush_rewrite_rules();
}