<?php

/**
 * Rotate each string characters by n positions in ASCII table
 * To encode use positive n, to decode - negative.
 * With n = 13 (ROT13), encode and decode n can be positive.
 *
 * @param string $string
 * @param integer $n
 * @return string
 */
function rotate($string, $n) {

    $length = strlen($string);
    $result = '';

    for($i = 0; $i < $length; $i++) {
        $ascii = ord($string{$i});

        $rotated = $ascii;

        if ($ascii > 64 && $ascii < 91) {
            $rotated += $n;
            $rotated > 90 && $rotated += -90 + 64;
            $rotated < 65 && $rotated += -64 + 90;
        } elseif ($ascii > 96 && $ascii < 123) {
            $rotated += $n;
            $rotated > 122 && $rotated += -122 + 96;
            $rotated < 97 && $rotated += -96 + 122;
        }

        $result .= chr($rotated);
    }

    return $result;
}

$enc = rotate('j-o-s-h-[-a-t-]-t-h-e-n-u-l-l-b-y-t-e-[-d-o-t-]-o-r-g', rand(1,25));

?>