you must use some code like this:
<html>
<head><title>List</title></head>
<body>
<form action="<?php echo $PHP_SELF ?>" method="post">
List:<textarea name='text' cols="50" rows="10"></textarea>
<input type="submit" value="Submit!" />
<input type="hidden" name="submited" value="true" />
</form>
<?php
if($submited){
$tmp=explode("\n",$text);
$list='<UL>';
for($i=0;$i<count($tmp);$i++)
$list.="<LI>".$tmp[$i]."</LI>";
$list.='</UL>';
echo $list;
}
?>
</body>
</html>