Need urgent help in PHP!

Hi, here's the deal. I applied to a job as a webdeveloper (I've previously studied Webdesign for a year), and one of the criterias was to have experience in PHP, which I have. Still, I pretty much only know some basic stuff.

I was contacted by them and I was told they wanted me to do something in PHP until monday so I can show them I at least know of it, so what I'm asking from you people here is to give me a few pointers as to what kind of things you would like to see if it were you that were hiring. Nothing too big, but not too simple, just enough to show I grasp the concept of PHP. I'm not asking you to script anything for me, I want to actually learn from it, just what kind of stuff I could do, tutorials are always good I'd be grateful for any tips, cause I really want this job.

Thanks in advance

make a password protected section of a website, storing and retrieving login credentials in a mysql database.