I'm building a small CMS in PHP for a client and something I've noticed that comes up fairly often is a client will enter a bit of HTML in a field without closing his/her tag. I'm wondering if there is some parsing technique to prevent bad HTML from rendering my whole output page in italics because the user forgot to add a closing </i> tag.

I'm not worried about XSS or malicious html, just a forgotten tag here and there as it's the client who is managing the content.

Forgive me if this is a duplicate question, I did some searching, but could not find an appropriate answer.

-J