Is there a php function that will encrypt a url string, so I'm not showing the world my data in the url?
If you must use the GET method for your form submit instead of a POST, you could use the base64_encode() and base64_decode() functions to at least make the value data look garbled...
like:
http://site.com/index.php?string='WW91ciBTZWNyZXQgTWVzc2FnZSAtIHNhdXNhZ2U='
