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
}