index.php

<?php

namespace DesignPatterns\Behavioral\Command;

include_once 'User.php';

$user = new User();

echo $user->compute('+', 100); // result = 100 (after + with 100)
echo $user->compute('-', 50); // result = 50 (after - with 50)
echo $user->compute('*', 10); // result = 500 (after * with 10)
echo $user->compute('/', 2); // result = 250 (after / with 2)

$levels = 4;
echo "Repeat $levels operation\n";
echo $user->undo($levels);
/* Repeat 4 operation
result = 500 (after * with 2)
result = 50 (after / with 10)
result = 100 (after + with 50)
result = 0 (after - with 100)
*/

$levels = 3;
echo "Cancel $levels operation\n";
echo $user->redo($levels);
/* Cancel 3 operation
result = 100 (after + with 100)
result = 50 (after - with 50)
result = 500 (after * with 10)
*/