WordPress Generate Structured Menu Helper Function

functions.php

<?php

// Takes in a WP Menu array (typically creatd by wp_get_nav_menu_items()) and returns
// a structured associative array of the menu items.
// Currently supports up to 3 levels of menu items.

function generate_structured_menu($wp_nav_items)
{
    $nav_items_structured = [];
    // Initial pass to add all parent items
    foreach ($wp_nav_items as $wp_nav_item) {
        if ($wp_nav_item->menu_item_parent == 0) {
            $nav_items_structured[$wp_nav_item->ID] = (array) $wp_nav_item;
            $nav_items_structured[$wp_nav_item->ID]["child_count"] = 0;
            $nav_items_structured[$wp_nav_item->ID]["grand_child_count"] = 0;
        }
    }
    // Second pass to add all 2nd tier child items
    foreach ($wp_nav_items as $wp_nav_item) {
        if ($wp_nav_item->menu_item_parent != 0) {
            // Add this as a child element if its parent item is present
            if (isset($nav_items_structured[$wp_nav_item->menu_item_parent])) {
                $nav_items_structured[$wp_nav_item->menu_item_parent][
                    "children"
                ][$wp_nav_item->ID] = (array) $wp_nav_item;
                // Update child count of the parent item
                $current_child_count = 0;
                if (
                    isset(
                        $nav_items_structured[$wp_nav_item->menu_item_parent][
                            "child_count"
                        ]
                    )
                ) {
                    $current_child_count =
                        $nav_items_structured[$wp_nav_item->menu_item_parent][
                            "child_count"
                        ];
                }
                $current_child_count++;
                $nav_items_structured[$wp_nav_item->menu_item_parent][
                    "child_count"
                ] = $current_child_count;

                // Set initial value for the child count of this item, if not already set
                $current_child_count = 0;
                if (
                    isset(
                        $nav_items_structured[$wp_nav_item->menu_item_parent][
                            "children"
                        ][$wp_nav_item->ID]["child_count"]
                    )
                ) {
                    $current_child_count =
                        $nav_items_structured[$wp_nav_item->menu_item_parent][
                            "children"
                        ][$wp_nav_item->ID]["child_count"];
                }
                $nav_items_structured[$wp_nav_item->menu_item_parent][
                    "children"
                ][$wp_nav_item->ID]["child_count"] = $current_child_count;
            }
        }
    }
    // Third pass to add all 3rd tier child items
    foreach ($wp_nav_items as $wp_nav_item) {
        // Traverse the child items of each parent array in the structured array
        foreach ($nav_items_structured as $nav_structured_item) {
            if (isset($nav_structured_item["children"])) {
                foreach (
                    $nav_structured_item["children"]
                    as $second_tier_child_item
                ) {
                    // $second_tier_child_item is array->parent_item->child_item
                    if (
                        $wp_nav_item->menu_item_parent ==
                        $second_tier_child_item["ID"]
                    ) {
                        $nav_items_structured[$nav_structured_item["ID"]][
                            "children"
                        ][$second_tier_child_item["ID"]]["children"][
                            $wp_nav_item->ID
                        ] = (array) $wp_nav_item;

                        // Update child count of the parent items
                        $current_grand_child_count = 0;
                        $current_child_count = 0;
                        if (
                            isset(
                                $nav_items_structured[
                                    $nav_structured_item["ID"]
                                ]["grand_child_count"]
                            )
                        ) {
                            $current_grand_child_count =
                                $nav_items_structured[
                                    $nav_structured_item["ID"]
                                ]["grand_child_count"];
                        }
                        if (
                            isset(
                                $nav_items_structured[
                                    $nav_structured_item["ID"]
                                ]["children"][$second_tier_child_item["ID"]][
                                    "child_count"
                                ]
                            )
                        ) {
                            $current_child_count =
                                $nav_items_structured[
                                    $nav_structured_item["ID"]
                                ]["children"][$second_tier_child_item["ID"]][
                                    "child_count"
                                ];
                        }
                        $current_grand_child_count++;
                        $current_child_count++;

                        $nav_items_structured[$nav_structured_item["ID"]][
                            "grand_child_count"
                        ] = $current_grand_child_count;
                        $nav_items_structured[$nav_structured_item["ID"]][
                            "children"
                        ][$second_tier_child_item["ID"]][
                            "child_count"
                        ] = $current_child_count;
                    }
                }
            }
        }
    }

    return $nav_items_structured;
}