Goatella/PHPTemperatureConversion — pull request #2 by moonandfox (2014-03-12 04:15:28+00:00)
Title: Add checks that input exists and is valid.

Check that input exists to avoid the 'undefined key' error that was occurring on initial page load due to the use of $_GET['scale'] and $_GET['degree'] before they existed.

Check that the input is not NULL or NaN. Prints error message if so, and displays it until valid input is entered.