In a lot of places in my code, is being shown an empty anchor tag.
<a> </a>
I've already searched for var_dump, print_r, error_log and such and couldn't find the source of this empty anchor. It's shown in my header, footer, everywhere. So, o started thinking about something more global like the_content filters or something like that.
How do I debug this situation?
I found the answer here. Indeed, just because I forgot to close ONE <a> SOMEWHERE in the code, everything was messed up.
I know you've already found your answer, but the way to debug these HTML problems is generally to push your HTML through the W3C validator. Not your PHP code, mind you, but the HTML as it appears when you show page source from the browser. It will spit out piles and piles of errors, but the crucial one is usually easily identified near the top. As a bonus, you then see all the other invalid elements of your HTML and can clean them as well.