What is "new line" depends on OS and, sometimes, where you use it. For example, in Windows, new line is CR LF (\r\n), but in MessageBox, either of these characters along acts as a new line. In edit controls, it would not work.
Please see: http://en.wikipedia.org/wiki/New-line
Most usually, PHP is used as a server-side script in Web applications, and, even more typically, it generates HTML HTTP output. But in HTML '\n' is not a new line, it is а… blank character. New line is
. Well, in case you did not know…