Pretty good article.
There's a little bug in your SQL injection though. I don't think the SQL injection you come up with would work correctly.
As you see, you're comparing an integer (1) with a character/string ('1') I'm not sure if SQL cares about it or not, but I'd prefer to compare a character/string and a character/string.
It was only a little note, beside that; good work!
I actually made a
blogpost on this topic a while ago, if anyone should be interested.