escaping ?>

I'm trying to do some string replaces on XML files to import them into a prprietary db that doesn't understand XML. I need to strip the XML tags out of the file. However, when I use this line: $contents = str_replace('<?xml version="1.0"?>', '', $contents); The ?> in the string ends my php block. I know there's an easy answer to this, and I'm probably just suffering from Friday afternoon burnout, but can someone let me know how to escape those so that I can search for them in the string? thanks, Steven