One-off tool to uncancel an order in magento 1.x

order-uncancel.php

<?php
 if(php_sapi_name()!=="cli"){
 echo "Must be run from the commend line.";
 };
/**
 * Setup a magento instance so we can run this export from the command line.
 */
require_once('app/Mage.php');
umask(0);
if (!Mage::isInstalled()) {
    echo "Application is not installed yet, please complete install wizard first.";
    exit;
}
// Only for urls // Don't remove this
$_SERVER['SCRIPT_NAME'] = str_replace(basename(__FILE__), 'index.php', $_SERVER['SCRIPT_NAME']);
$_SERVER['SCRIPT_FILENAME'] = str_replace(basename(__FILE__), 'index.php', $_SERVER['SCRIPT_FILENAME']);
Mage::app('admin')->setUseSessionInUrl(false);
Mage::setIsDeveloperMode(true); ini_set('display_errors', 1); error_reporting(E_ALL);
try {
    Mage::getConfig()->init();
    Mage::app();   
} catch (Exception $e) {
    Mage::printException($e);
}
ini_set('memory_limit','500M');

try{
  //@see http://magento.stackexchange.com/questions/7254/is-there-any-way-to-get-back-the-cancelled-order#comment189623_7255  
  $incrementId = '100000835'; //replace this with the increment id of your actual order
  $order = Mage::getModel('sales/order')->loadByIncrementId($incrementId);

  $order->setState(Mage_Sales_Model_Order::STATE_PROCESSING);
  $order->setStatus('pending');
  $order->setBaseDiscountCanceled(0);
  $order->setBaseShippingCanceled(0);
  $order->setBaseSubtotalCanceled(0);
  $order->setBaseTaxCanceled(0);
  $order->setBaseTotalCanceled(0);
  $order->setDiscountCanceled(0);
  $order->setShippingCanceled(0);
  $order->setSubtotalCanceled(0);
  $order->setTaxCanceled(0);
  $order->setTotalCanceled(0);

  foreach($order->getAllItems() as $item){
      $item->setQtyCanceled(0);
      $item->setTaxCanceled(0);
      $item->setHiddenTaxCanceled(0);
      $item->save();
  }

  $order->save();
  echo "Order $incrementId has been un-canceled\n";

} catch (Exception $e) {
    //$response['error'] = $e->getMessage();
    Mage::printException($e);
}