Les chaines de caractères en php - quest WCS

<?php

$messages = ["0@sn9sirppa@#?ia'jgtvryko1", "q8e?wsellecif@#?sel@#?setuotpazdsy0*b9+mw@x1vj", "aopi?sgnirts@#?sedhtg+p9l!"];

$results = [];
foreach ($messages as $key => $message) {
    $results[$message]['keyNumber'] = strlen($message) / 2;
    $results[$message]['subString'] = substr($message, 5, $results[$message]['keyNumber']);
    $results[$message]['replacedString'] = str_replace('@#?', ' ', $results[$message]['subString']);
    $results[$message]['decodedMessage'] = strrev($results[$message]['replacedString']);
    echo $results[$message]['decodedMessage'];
}