New lines in textarea

Hello once again, new bug :) When a user completes a Textarea tag, he may want to insert some new lines, which should be interpreted well by the script. I store all the data in a file, and I need to replace all the new line signs with <BR> tags. I tried nl2br() and ereg_replace("\n", "<BR>", $str). They both don't work properly. So the question is what kind of symbols are added along with "\n" by browsers once the form is completed on a site. Thanx!