URLencode returns a string in which all non-alphanumeric characters
except -_. have been replaced with a percent (%)
sign followed by two hex digits and spaces encoded as plus (+)
signs. It is encoded the same way that the posted data from a WWW form
is encoded, that is the same way as in
application/x-www-form-urlencoded media type.
urldecode decodes any %##
encoding in the given string.