One Time Pad

one-time-pad.php

<?php
$ls = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
$ks = strtoupper('horsebounceauburnrooseveltbeepswapnoreastersatchelcuriousdunamiswintermintrubikdandermystifyapogeefranciscandiminish');
$vs = [];

function encode($str) {
    $str = strtoupper(preg_replace('/[^a-zA-Z]/', '', $str));
    global $ls, $ks;
    $n = [];
    foreach (str_split($str) as $k => $c) {
        $n[] = $ls[(array_search($ks[$k],$ls)+array_search($c,$ls))%25];
    }
    return implode('', $n);
}

function decode($str) {
    $str = strtoupper(preg_replace('/[^a-zA-Z]/', '', $str));
    global $ls, $ks;
    $n = [];
    foreach (str_split($str) as $k => $c) {
        $num = (array_search($c,$ls)-array_search($ks[$k],$ls))%25;
        if ($num < 0):
            $num = 25 - ($num*-1);
        endif;
        $n[] = $ls[$num];
    }
    return implode('', $n);
}

if ( array_key_exists(1,$argv)):
    if ( ! array_key_exists(2,$argv)):
        die('String required.');
    endif;
    switch ($argv[1]) {
        case 'encode':
            $output = encode($argv[2]);
            break;
        case 'decode':
            $output = decode($argv[2]);
            break;
        default:
            die('Invalid command.');
    }
    echo $output . "\n";
else:
    die('Command required. Try `encode` or `decode`.');
endif;