I figured it out. Putting double quotes around the <span> tags seemed to do the trick.
Pastebin
There’s a link to my header.php
Line 30 is the wp_nav_menu function. I’m not exactly sure what you mean by that.
Should I put the ?> tag right before the ‘<span>’ tags and reopen <?php right after them?
I have very little experience with php, so I’m not that great with the syntax yet…