Class ‘DOMDocument’ not found

This will happen when a class that the sanitiser relies on is not installed on your server. Unfortunately this isn’t something we can help with but these posts should help point you in the right direction.

XML Headers Appearing Inline

If you’ve added a file before activating WP SVG you may still have XML headers in your SVG file. These don’t play so well when inlined into HTML so you can use a function like the below to fix this,