ROT13 implementation with php://filter

rot13.filter.php

<?php

    /**
     * ROT13 implementation with php://filter
     *
     * @see    http://php.net/manual/en/wrappers.php.php
     * @param  string $message
     * @return string
     */
    function rot13_filter($message)
    {
        return file_get_contents("php://filter/string.rot13/resource=data:text/plain,{$message}");
    }

    $message = 'Hello Word';
    $encode  = rot13_filter($message);
    $decode  = rot13_filter($encode);

    print "{$encode}\n{$decode}\n";