<section class="slider">

    <?php if( have_rows('promotion') ): ?>

        <div id="slider" class="flexslider">

            <ul class="slides">

            <?php while ( have_rows('promotion') ) : the_row(); ?>

                <li>

                    <?php $post_object = get_sub_field('promotion');

                    if( $post_object ):
                    $post = $post_object; setup_postdata( $post );
                    the_title();
                    echo get_the_id();
                    wp_reset_postdata();

                   endif; ?>

                </li>

            <?php endwhile; ?>

            </ul>

        </div>

    <?php endif; ?>

</section>
<section class="slider">

    <?php if( have_rows('blocks') ): ?>

        <div id="slider" class="flexslider">

            <ul class="slides">

            <?php while ( have_rows('blocks') ) : the_row(); ?>

                <li>

                    <?php $post_object = get_sub_field('block');
                    if( $post_object ):
                    $post = $post_object; setup_postdata( $post );
                    the_title();
                    echo get_the_id();
                    wp_reset_postdata();

                   endif; ?>
                </li>

            <?php endwhile; ?>

            </ul>

        </div>

    <?php endif; ?>

</section>