php – WordPress link obfuscation without base64_decode

Currently we are developing a WordPress theme and one of the requirements is to have the backlink in the footer obfuscated.

We tried encoding the HTML using a PHP obfuscation tool, but when we tried to verify the theme for errors – the reply was that using base64_decode is not allowed for publishing to the WordPress theme market.

What would be the best way to actually encode the HTML so that the backlinks are not easily removable from the footer?

Thanks in advance.