A RFC3986 compliant function for decoding URLs, originally written with intent to be used in a CGI application. It takes strings like https%3A%2F%2Fwww.google.ca%2F%3Fgws_rd%3Dssl%23q%3Durl%2Bdecoding and turns it into strings like https://www.google.ca/?gws_rd=ssl#q=url+decoding for query string processing.
Note that it doesn't convert +'s to spaces(as per the spec), it's expected that the programmer does this on their own.