Here is what I had for a PAL BOX solution, it is nothing special.
It could probably be upgraded to grab your current page, update the language using a "languageupdate.php" page, and then redirect you back to the page you were on. You could then use this potentially in the menubar up top, or similar areas.
A few notes - there are THREE variables you have to fill in up top. The custompalbox you are going to place this in (the file calls itself), the title, and your PATH to main.inc.php. Again note, if you are using this for 6.5, you need to update that path to allow the includes folder!
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