Shoutbox

I'm trying to make a webpage, that loads the info from my database, that works fine, and putting info in the database with my self made php works too. But i only want one row, so if i put new info in the database it overwrites the old info.

I read on the mysql page i have to use this:

code:

---

mysql> INSERT INTO table (a,b,c) VALUES (1,2,3)
    -> ON DUPLICATE KEY UPDATE c=c+1;
mysql> UPDATE table SET c=c+1 WHERE a=1;

---

But i don't undertand it , can someone help me?

TIA