Highlight active Admin Menu when added though add_menu_page

add_filter( ‘parent_file’, ‘parent_file_hover’ );
function parent_file_hover( $parent_file ) {
global $pagenow;
if ( $pagenow == ‘post.php’)
$parent_file = “post.php?post={$_REQUEST[‘post’]}&action=edit”;
elseif($pagenow == ‘post-new.php’)
$parent_file = “post-new.php?post_type={$_REQUEST[‘post_type’]}”;
return $parent_file;
}