<div class="container-fluid mt-5">
    <div class="row">
        <div class="col-12">
            <form action="<?php echo admin_url('admin-post.php') ?>" method="POST">
                <input type="hidden" name="action" value="salva_impostazioni_layout">
                <input type="hidden" name="layout" value="<?php echo $_GET['layout'] ?>">
                <input type="submit" class="btn btn-primary" value="<?php _e("Use this layout",'syrus') ?>">
            </form>
        </div>
    </div>
</div>