php if statement detecting [href=""]

im a bit new with php and i have a problem that should be small but i cant figure it out.

i have a wordpress page with 2 links in every post. i want to show the links only if there is a address in the href="". otherwise i want them to stay invisible/disappear.

<span class="play"><a rel="lightbox" href="<?php swf_file_url(); ?>">Play</a></span>
<span class="download"><a href="<?php swf_file_url(); ?>" download>Download</a></span>

anyone know a simple way of doing this?