security, receiving html from a form

For my website I created an updating system in php. Where my staff and I can write articles that then get saved to the server, linked to, etc. I allowed html to be passed from the form because a lot of the staff likes to use html tags in their articles. Which I know is a security issue. I know I could use HTMLSpecialChars() and then devise my own mark up system; which I will if I have no other alternative. But I was wondering if just searching the article string for "<?", "?>", "<script", etc and not writing the file if they're found would suffice. That almost seems too simple though. Thanks, Matt