3v4l.org

run code in 300+ PHP versions simultaneously
<?php $data = ['a' => 'n%20n']; foreach($data as $k => $v) { print urlencode(urldecode($k)) . '=' . urlencode(urldecode($v))."\n"; } print http_build_query($data)."\n";

preferences:
57.12 ms | 402 KiB | 5 Q