PHP XSS Prevention WhiteListing

Question

My site utilizes a WYSIWYG editor for users to update their accounts,enter comments, and send private messages.

The editor (CKEditor) is great for only allowing users to enter valid input, but I worry about injection through TamperData or other means.

How can I control this on the server side?

I need to whitelist specific tags: <b><ul><ol><a><img><br>, will this be a SAFE approach to preventing XSS?

Answer 1

strip_tags is going to be your friend. The second parameter lets you pass in an array of allowed tags strip_tags

Answer 2

Use HTML Purifier:

HTML Purifier is a standards-compliant HTML filter library written in PHP. HTML Purifier will not only remove all malicious code (better known as XSS) with a thoroughly audited, secure yet permissive whitelist.