write file

[eluser]Colin Williams[/eluser]
[url="http://us2.php.net/copy"]copy('/path/to/src', '/path/to/dest')[/url]

So, very basically, it would look like

Code:

$new_lang = $_POST['new_lang'];

$src = APPPATH .'language/english/filename'. EXT;
$dest = APPPATH .'language/'. $new_lang .'/filename'. EXT;

copy($src, $dest);