As deliteblogger said, be sure to use double quotes for your newline.

PHP Code: 
<?php
$newline 
"\n";
$text 'Hello world';

echo 
'<textarea>';

echo 
$text $newline// -> Hello world + newline
echo $text "\n"// -> Hello world + newline
echo 'Hello World' "\n"// -> Hello world + newline

echo '</textarea>';
?>
Those three ways will work.