在wp_nav_menu()中访问页面的ACF字段

// functions.php

// 创建自定义字段组
function my_acf_fields() {
    acf_add_local_field_group(array(
        'key' => 'group_1',
        'title' => 'ACF Fields',
        'fields' => array(
            array(
                'key' => 'field_1',
                'label' => 'Custom Field',
                'name' => 'custom_field',
                'type' => 'text',
            ),
        ),
        'location' => array(
            array(
                array(
                    'param' => 'post_type',
                    'operator' => '==',
                    'value' => 'page',
                ),
            ),
        ),
    ));
}
add_action('acf/init', 'my_acf_fields');

// header.php

// 生成导航菜单
wp_nav_menu(array(
    'theme_location' => 'primary',
    'walker' => new ACF_Walker_Nav_Menu(),
));

// 自定义导航菜单Walker类
class ACF_Walker_Nav_Menu extends Walker_Nav_Menu {
    // 重写display_element()方法
    function display_element($element, &$children_elements, $max_depth, $depth, $args, &$output) {
        // 获取当前页面的ACF字段的值
        $custom_field = get_field('custom_field', $element->object_id);
        
        // 添加ACF字段的值到导航菜单项
        $element->title .= ' (' . $custom_field . ')';
        
        // 调用父类的display_element()方法
        parent::display_element($element, $children_elements, $max_depth, $depth, $args, $output);
    }
}