Request continuation for confirmation page

RequestContinuation.php

<?php
/**
 * Request continuation
 *
 * This utility provides a very short lifetime (and navigation closed) session.
 * Confirmation page shown after user input form should hold previously poted
 * data and passes them to the next request. Those data would live in only two
 * requests, so they should be in request scope.
 * It's bad idea to use cookie or _SESSION to implement for confirmation page!
 *
 * CONFIRMATION PAGE:
 * <input type="hidden"
 *        name="encoded_prev_post"
 *        value="<?php echo htmlspecialchars(RequestContinuation::encode($_POST));?>" />
 * <input type="submit" value="commit" />
 *
 * COMMIT/MODIFY ACTION:
 * $prev_post = RequestContinuation::decode($_POST['encoded_prev_post']);
 *
 */
class RequestContinuation {
    /**
     * @param $data array
     * @return string
     */
    public static function encode($data) {
        return http_build_query($data);
    }
    /**
     * @param $data string
     * @return array
     */
    public static function decode($data) {
        parse_str($data, $buf);
        return $buf;
    }
}