[mysql - php] Newline to BR problem

I'm trying to place a text from a textfield into a database and displaying it on another page. All works fine and well but my problem is: If i place newline characters (press enter) in the forms textfield they don't show up on my display page. This is logical because newlines are not <br> codes. So i must replace the newline thingies with <br> code. Should this be done BEFORE i put the text in the database or AFTER i put the text in the database and what functions can i use???? Maybe it's a newbie question but it's on my mind for a few days now and i haven't found an answer yet, thanx!