我是WordPress的OOP新手，可能需要一些帮助来调试这个问题。我一直在寻找答案，并试图调试自己，但可能需要一只手。我正在尝试创建管理菜单项及其页面，但出现以下错误：

Whoops\\Exception\\ErrorException thrown with message "call_user_func_array() expects parameter 1 to be a valid callback, function \'create_admin_page\' not found or invalid function name"

有人能帮我指出正确的方向吗？提前感谢！

这是我的班级。

namespace MyNamespace;


class MyClass {


    public function __construct() {
        add_action(\'admin_menu\', array($this, \'create_menu_item\'));
        //add_action(\'admin_bar_menu\', \'remove_wp_logo\', 999);
        //add_filter( \'admin_bar_menu\', \'change_howdy\', 25 );

        ddd($this->create_menu_item());


    }

//Get all pages

    public function get_all_pages() {
        $allpages = get_pages( array( \'post_type\' => \'page\', \'posts_per_page\' => \'-1\') );
        return $allpages;

    }

    //Get Parent Page ID
    protected function get_location_id() {
        $parents = get_page_by_title(\'Locations\');        
        return  $parents->ID;
    }

    //Get all locations excluding grandchildren
    protected function get_top_level_pages() {
        $children = get_page_children( $this->get_location_id(), $this->get_all_pages() );
        $locations = array();
        foreach ($children as $key => $value) {
            if ($this->get_location_id() == $value->post_parent) {
                $locations[$key] = $this->{$key} = $value;
            }
        }
        return $locations;
    }
    //Create top level menu item
    public function create_menu_item() {

        $locations = $this->get_top_level_pages();
        foreach ($locations as $key => $value) {
            add_menu_page( 
                $value->post_title, 
                $value->post_title, 
                \'manage_options\', 
                $value->post_name.\'-admin-page.php\', 
                \'create_admin_page\', //here is where I am calling the next function
                \'dashicons-location-alt\', 
                6  
            );

        }

    }

//Create Admin Page -----should be it\'s own class? 
    public function create_admin_page() {
        $children = get_page_children( $this->get_location_id(), $this->get_all_pages() );
        ?>
        <div class="wrap">
            <h2>Welcome Child Pages</h2>
        </div>
            <ul>
            <?php 
                if(!empty($children)){
                    echo \'<ul>\';
                    foreach($children as $child){
                        echo \'<li><a href="\'.get_permalink($child->ID).\'">\'.$child->post_title.\'</a></li>\';
                    }
                    echo \'</ul>\';
                }    
            ?>
            </ul>
        <?php

    }