Decodes any %## encoding in the given string. Plus symbols ('+') are decoded to a space character.
[ PHP.net urlencode - PHP.net urldecode ]

$str = '?x=te s/t';
$encoded = urlencode($str);
> %3Fx%3Dte+s%2Ft

$decoded = urldecode($encoded);
> ?x=te s/t