我已经测试了您的代码，如果您在init 行动挂钩。在您的代码中，我没有看到注册post类型的操作挂钩。Cna你试试这个？（请记住在更新代码后刷新rewirte规则。请注意，我删除了未定义的变量$labels 在$args 分类法数组）：

add_action(\'init\', \'cyb_register_post_type_and_taxonomies\');
function cyb_register_post_type_and_taxonomies() {
    register_post_type( \'city\',
                        array(
                            \'labels\' => 
                                array(
                                    \'name\' => \'City Guides\',
                                    \'singular_name\' => \'City Guides\',
                                    \'add_new\' => \'Add New\',
                                    \'add_new_item\' => \'Add New retailer\',
                                    \'edit\' => \'Edit\',
                                    \'edit_item\' => \'Edit retailer\',
                                    \'new_item\' => \'New retailer\',
                                    \'view\' => \'View\',
                                    \'view_item\' => \'View retailer\',
                                    \'search_items\' => \'Search retailers\',
                                    \'not_found\' => \'No retailer found\',
                                    \'not_found_in_trash\' => \'No Shop retailer in Trash\',
                                    \'parent\' => \'Parent retailer\'
                                ),
                            \'public\' => true,
                            \'menu_position\' => 6,
                            \'supports\' => array( \'title\', \'editor\', \'thumbnail\' ),
                            \'has_archive\' => true,
                            \'taxonomies\' => array(\'city_categories\'),
                            \'can_export\' => true,
                            \'rewrite\' => array(\'slug\'=>\'travel\')
                         )
    );
    $args = array( 
            \'labels\' => array(),
            \'public\' => true,
            \'show_in_nav_menus\' => true,
            \'show_ui\' => true,
            \'show_tagcloud\' => true,
            \'show_admin_column\' => true,
            \'hierarchical\' => true,
            \'rewrite\' => true,
            \'query_var\' => true
    );

    register_taxonomy( \'city_categories\', array(\'city\'), $args );

    $args = array(
            \'labels\' => array(), // defined correctly, shortened the code
            \'public\' => true,
            \'show_in_nav_menus\' => true,
            \'show_ui\' => true,
            \'show_tagcloud\' => true,
            \'show_admin_column\' => true,
            \'hierarchical\' => true,
            \'rewrite\' => true,
            \'query_var\' => true,
            \'sort\' => true
    );

    register_taxonomy( \'cities\', array(\'city\'), $args );
}

听起来您的重写规则仍有问题，请尝试添加flush_rewrite_rules() 在包含您在问题中发布的注册呼叫的函数末尾。像这样：

flush_rewrite_rules( false );

But 不要忘记在测试后从代码中删除这一行，否则每次调用站点时都会执行这一行，这很糟糕，您当然不希望这样。