Multiline String variable

Have a .php service file that creates a file from App's parameters sended to it:

<?php

$getVar = $_POST['TheString'];

$file = 'test.txt';

$writeVar = fopen($file,'w');

fwrite($writeVar,$getVar);

fclose($writeVar);

?>

and the collection of AS service functions to send parameters.

        private function sendData(str:String):void {
            variables = new URLVariables();
            fData = new URLRequest("fileservices/SaveService.php");
            fData.method = URLRequestMethod.POST;
            fData.data = variables;
            fLoader = new URLLoader();
            fLoader.dataFormat = URLLoaderDataFormat.VARIABLES;
            fLoader.addEventListener(Event.COMPLETE, sendComplete);
            variables.TheString = str;
            fLoader.load(fData);
        }

All works, but can only write a single-line string into a file.

when send a string containing '/n' paragraph character, it does not work in .txt file opened with Notepad.

So, what is that specific character to use to mark paragraphs returns,

or should i use the different class instead of String,

or have i to edit my .php file to add such usability (and what is that magic changes to bring)?

Thanks in advance