If Image's caption parameter ir empty, use title instead. Else, use caption

I'm setting up a gallery. If the image has an external link (using caption for input), it should follow the link. If not, it should follow the image url. I've got this, but it's not working.

<?php if $image['caption'] === '': ?>
    <a href="<?php echo $image['url']; ?>" style="background-image:url(<?php echo $image['url']; ?>)"/>
<?php else: ?>
    <a href="<?php echo $image['caption']; ?>" style="background-image:url(<?php echo $image['url']; ?>)"/>
<?php endif; ?>

I also thought this might've worked, but didn't:

<?php if empty($image['caption']): ?>

How can I accomplish this?