<?php

/* Functions */

function addspaces(&$string){
    $string = implode(' ', str_split($string));
}

function reverse(&$string){
    $string = strrev($string);
}

function setlower(&$string){
    $string = strtolower($string);
}

function setupper(&$string){
    $string = strtoupper($string);
}

/* Main script */

$str = $_GET['merkkijono'];

switch($_GET['mode']){
    case 1:
        addspaces($str);
        setlower($str);
    break;

    case 2:
        addspaces($str);
        setupper($str);
    break;

    case 3:
        reverse($str);
        setlower($str);
    break;

    case 4:
        reverse($str);
        setupper($str);
    break;
}
echo $str;
?>