Store and restore the states of objects

state_archivist.php

<?php
/**
 * Optional convenience class. Objects extending the
 * StateHandler class can register with a StateArchivist
 * instance; then calling remember() or restore() on the 
 * archivist will be propagated to all registered objects.
 */
class StateArchivist {

  /**
   * The array of objects
   * @var array
   */
  private $objects = [];

  /**
   * Register an object that extends the StateHandler 
   * class and initially have it remember its state 
   * (unless specified otherwise).
   * @param  StateHandler  $object
   * @param  boolean       $remember
   */
  public function register(
    StateHandler $object, 
    $remember = true
  ) {

    if ($remember) {
      $object->remember(); 
    }

    $this->objects[] = $object;
  }

  /**
   * Call the remember() function on
   * all registered objects
   */
  public function remember() {

    foreach ($this->objects as $object) {
      $object->remember();
    }
  }

  /**
   * Call the restore function on all objects
   */
  public function restore() {

    foreach ($this->objects as $object) {
      $object->restore();
    }
  }
}
?>

state_handler.php

<?php
/**
 * Objects extending this class can remember
 * and later restore their state
 */
class StateHandler {

  /**
   * The array of states
   * @var array
   */
  private $states = [];

  /**
   * Optionally takes an instance of a StateArchivist
   * as parameter where it immediately registers itself
   * @param StateArchivist|null $archivist
   */
  public function __construct(StateArchivist $archivist = null) {

    if ($archivist) {
      $archivist->register($this);
    }
  }

  /**
   * Store the current state
   */
  public function remember() {
    $state = get_object_vars($this);

    unset($state['states']);
    $this->states[] = $state;
  }

  /**
   * Restore the last state
   */
  public function restore() {
    $state = array_pop($this->states);

    if (!$state) return;

    foreach ($state as $key => $value) {
      $this->$key = $value;
    }
  }  
}
?>

Sample usage:

<?php
class Counter extends StateHandler {
  public $count = 0;

  public function increment() {
    return ++$this->count;
  }
}

$archivist = new StateArchivist();
$counter = new Counter($archivist);

echo $counter->increment() . PHP_EOL; // 1
$archivist->remember();
echo $counter->increment() . PHP_EOL; // 2
$archivist->restore();
echo $counter->count . PHP_EOL;       // 1
$archivist->restore();
echo $counter->count . PHP_EOL;       // 0
?>

License

MIT