How to add next height number in Order Attributes inside the Add new page. [duplicate]

add_action( 'admin_footer', 'my_action_javascript' ); // Write our JS below here
function my_action_javascript()
    global $wpdb;
    $pageposts = $wpdb->get_var("SELECT max(menu_order) FROM $wpdb->posts WHERE post_status="publish" AND post_type="post_trainers"");
    ?>

<script type="text/javascript" >
    jQuery(document).ready(function($) {

        var data = {
            'action': 'my_action',
            'whatever': <?=$pageposts?>
        };

        $.post(ajaxurl, data, function(response) {
               if($('#menu_order').val()=='' || $('#menu_order').val()=='0')
                $('#menu_order').val(response);
        });
    });
</script> <?php
}

add_action( 'wp_ajax_my_action', 'my_action_callback' );
function my_action_callback() {
global $wpdb; // this is how you get access to the database

$whatever = intval( $_POST['whatever'] );

$whatever += 1;
echo $whatever;
wp_die(); // this is required to terminate immediately and return a proper response
}

I was fix this issue Yesterday