如何在url中传递附加参数以使分页生效

我现有的页面链接是http://localhost/site/wp-admin/admin.php?page=myPage

如何在PHP中创建要添加的语法/逻辑&pagenum=1 在url中？

目前我有此代码

global $wpdb;

$per_page = 6;
$page_query = $wpdb->get_var("SELECT COUNT(\'id\') FROM form"); 

$pages = ceil($page_query / $per_page);

$currentPage = (isset ($_GET[\'pagenum\'])) ? (int)$_GET[\'pagenum\'] : 1;
$start = ($currentPage -1 ) * $per_page;

$row = $wpdb->get_results("SELECT * FROM form LIMIT $start , $per_page");

//foreach loop here