How can a user profile dropdown menu be added to a WordPress site using PHP?

To add a user profile dropdown menu to a WordPress site using PHP, you can utilize the `wp_nav_menu()` function along with a custom walker class to generate the dropdown menu. This allows you to display a list of user-specific links in a dropdown format within the site's navigation menu.

// Add user profile dropdown menu to WordPress navigation menu
function add_user_profile_dropdown_menu($items, $args) {
    if (is_user_logged_in() && $args->theme_location == 'primary') {
        $items .= '<li class="menu-item menu-item-has-children">';
        $items .= '<a href="#">Profile</a>';
        $items .= '<ul class="sub-menu">';
        $items .= '<li><a href="' . get_edit_profile_url() . '">Edit Profile</a></li>';
        $items .= '<li><a href="' . wp_logout_url() . '">Logout</a></li>';
        $items .= '</ul>';
        $items .= '</li>';
    }
    return $items;
}
add_filter('wp_nav_menu_items', 'add_user_profile_dropdown_menu', 10, 2);