- urldecode: documentation ( source)
- base64_encode: documentation ( source)
<?php
$url = 'http%3A%2F%2Fwww.my2.com%2Fapi.php%3Fkey1%3Dxxx%26key2%3Dyyy%26key3%3Dzzz';
echo $url.'<br>\n';
$url = urldecode($url);
echo $url.'<br>\n';
$url = base64_encode($url);
echo $url.'<br>\n';