Preventing links in form submissions through php.

I've been working on this for several days and haven't found an easy solution. I've created a simple question and answer form that uses PHP to load up a Subject and comment field. The comment field is very similar to the form I'm using to fill out this question. It's a simple Text Area box, the Subject is a simple Text Field box. Both are required and add to a MySQL database table that has an id, subject and comments table setup.

Now that I've got it up I'd like to prevent folks from adding links and scripts to both fields. I just want plain text, no <a href"my good stuff.com"> or malicious scripts. There's got to be a simple way of looking at the text in the fields and discovering < or > and then just redirecting them to an error page that says you can't post code here...

I've written code that validates e-mails addresses, but I can't seem to get a handle on looking for and failing any post that attempts to add a link.

Thanks for the help.