Long before I knew anything - not that I know much even now - I desgined a web app in php which inserted data in my mysql database after running the values through htmlent
Since PHP was the method of encoding, you'll want to use it to decode. You can use html_entity_decode to convert them back to their original characters. Gotta loop!
Just be careful not to decode rows that don't need it. Not sure how you'll determine that.