Hi!
Line Breaks can be generated by:
$myNewString = nl2br($myString);
...but I think you should not do this. When you insert text (with line breaks) from a textarea the line feed character will also be stored in the database.
You should better format this text AFTER output from database:
$result = mysql_query("select * from mytable");
while ($myRows=mysql_fetch_array($result)) {
echo nl2br($myRows[myColumn]) . "<BR>";
}