hi,

You can use nl2br().

Here's a simple example:
HTML Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>line breaks</title>
</head>

<body>
<?php
if (isset ($_POST['Submit']))
{
$input = $_POST['input'];
$input = nl2br ($input);
echo $input;
}
else
{
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="application/x-www-form-urlencoded" name="form1" target="_self" id="form1">
  <textarea name="input" id="input"></textarea>
  <br />
  <input type="submit" name="Submit" value="Submit" />
</form>
<?php
}
?>
</body>
</html>
Remember that there are some security measures that you should follow when receiving user input!