您使用GET是正确的，这可能是最容易使用的。

试试这个：

Add_Child_Page::on_load();

class Add_Child_Page {

    static function on_load() {

        add_action( \'init\', array( __CLASS__, \'init\' ) );
        add_action( \'admin_init\', array( __CLASS__, \'admin_init\' ) );
    }

    static function init() {

        add_action( \'admin_bar_menu\', array( __CLASS__, \'admin_bar_menu\' ), 90 );
    }

    static function admin_bar_menu( $wp_admin_bar ) {

        if( is_page() ) {

            $wp_admin_bar->add_node( array(
                \'id\'    => \'add_child_page\',
                \'title\' => \'Add Child Page\',
                \'href\'  => add_query_arg( array( \'post_type\'   => \'page\', \'page_parent\' => get_the_ID() ), admin_url( \'post-new.php\' ) ),
            ) );
        }
    }

    static function admin_init() {

        add_filter( \'page_attributes_dropdown_pages_args\', array( __CLASS__, \'page_attributes_dropdown_pages_args\' ) );
    }

    static function page_attributes_dropdown_pages_args( $dropdown_args ) {

        if ( ! empty($_REQUEST[\'page_parent\']) )
            $dropdown_args[\'selected\'] = (int) $_REQUEST[\'page_parent\'];

        return $dropdown_args;
    }
}