Function 'exif_imagetype' Not found.

The exif functions are basic php functions, and when this error message appears, that means they're not enabled in your server.

If you have access to your php.ini file, you should search for these values and enable them (by removing the semicolon before them):

extension=php_mbstring.dll
extension=php_exif.dll

If you don't have access to that file, you should contact your host and ask them to enable the exif extension for you.