How can I implement an "interesting tags" feature like that on Stack Overflow?

Check my other question with bounty: Finding similar number patterns in table

I'm trying to implement an Interesting Tags feature. For reference, this is how it works on SO:

1. I add into the "interesting" list my interested tags (like php, mysql, jquery and so on).
2. Then, if any of the displayed questions has some of the tags in my list, it makes the background orange.

I understand how to use jQuery to do that (there are related questions on that), but can't figure out how to implement the back-end portion using MySQL!

So here's my question: How is it done? I imagine it working like this:

• There is a row in mysql for every member, let's call it "interested_tags".
• After I write and submit my tag through input, it is being written in a row "interested_tags".

• Then, the main page has a query which shows all answers and it always checks question's tags with mine tags using strpos like this:

  if(strpos($question_tags, $my_tags) === true) {
     //and here will be made background orange
  }
  

Am I thinking right or is there any way to do it?

EDIT: So, can you show me an example or give me some tips how to implement this with many-to-many relationships? Thanks.