<?php
    $text = "The quick brown fox jumps over the lazy dog";
    $shift = 3;
    $alphabet = array("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");

    $n = count($alphabet);
    $char = strlen($text);
    $encode = array();

    for($i=0;$i<$char;$i++) {
        $encode[] = $text[$i];
    }

    foreach ($encode as $sym) {
        foreach ($alphabet as $alp) {
            if($sym == $alp) {
                $key = array_search($alp, $alphabet);
                if($key !== FALSE) {
                    $newkey = ($key + $shift) % $n;
                    echo $alphabet[$newkey];
                }
            }
            else if(($sym == mb_strtoupper($alp)) || ($sym == " ")) {
                echo $sym;
            }
        }
    }

    for($i=0;$i<$char;$i++) {
        for($s=0;$s<$n;$s++) {
            if($text[$i] == $alphabet[$s]) {
                $key = array_search($alphabet[$s], $alphabet);
                if($key !== FALSE) {
                    $newkey = ($key + $shift) % $n;
                    echo $alphabet[$newkey];
                    break;
                }
            }
            else if(($text[$i] == mb_strtoupper($alphabet[$s])) || ($text[$i] == " ")){
                echo $text[$i];
            }
        }
    }