- parse_str: documentation ( source)
- urldecode: documentation ( source)
- parse_url: documentation ( source)
<?php
$src = 'http://www.my.com/api.php?url=http%3A%2F%2Fwww.my2.com%2Fapi.php%3Fkey1%3Dxxx%26key2%3Dyyy%26key3%3Dzzz';
$src = parse_url($src);
parse_str( urldecode( $src['query'] ) );
echo $url;