查询IF语句时没有返回的变量值

Question

I've added a value to $old_pdf1, var dumped it to test and yep it's there. So I then added the elseif statement but now it will no longer show.

If I var_dump before the elseif statement it shows the URL I want, if I put it at the end it doesn't return anything.

<?php

$old_pdf1 = get_field('old_pdf_file_1');

if( have_rows('pdf_files') ): ?>

    <ul>

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

        <li><?php the_sub_field('case_study_pdf'); ?></li>

    <?php endwhile; ?>

    </ul>

<?php

    elseif( !empty($old_pdf1) ):
    the_field('old_pdf_file_1');
?>

<?php endif; ?>