Content migration in Craft example.

MyPlugin_MigrateManagerTask.php

<?php

namespace Craft;

class MyPlugin_MigrateManagerTask extends BaseTask
{

  private $_elements;

  /**
   * @inheritDoc ITask::getDescription()
   *
   * @return string
   */
  public function getDescription()
  {
    return Craft::t('Migrating old content');
  }

  /**
   * @inheritDoc ITask::getTotalSteps()
   *
   * @return int
   */
  public function getTotalSteps()
  {
    // Setup the criteria for finding the elements we want to migrate
    $criteria = craft()->elements->getCriteria(ElementType::Entry);
    $criteria->enabled   = null;
    $criteria->limit     = null;
    $criteria->status    = null;
    $criteria->sectionId = 15; // The ID of the section we are copying from
    $elements = $criteria->find();

    // Chunk the elements into groups of 10 - if the content is quite
    // light you may want to up this to 100 or so
    $this->_elements = array_chunk($elements, 10);

    return count($this->_elements);
  }

  /**
   * @inheritDoc ITask::runStep()
   *
   * @param int $step
   *
   * @return bool
   */
  public function runStep($step)
  {
    // I frequently found I ran out of memory doing these sort of operations
    // so just bumped up what Craft is allowed to use here - in this to 2.5GB
    craft()->config->set('phpMaxMemoryLimit', '2560M');
    craft()->config->maxPowerCaptain();

    // Run the migration as a sub Task with the current chunk of elements
    return $this->runSubTask('MyPlugin_Migrate', null, array(
      'elements' => $this->_elements[$step]
    ));
  }

}

MyPlugin_MigrateTask.php

<?php

namespace Craft;

class MyPlugin_MigrateTask extends BaseTask
{

  /**
   * @inheritDoc ITask::getDescription()
   *
   * @return string
   */
  public function getDescription()
  {
    return Craft::t('Migrating ...');
  }

  /**
   * @inheritDoc ITask::getTotalSteps()
   *
   * @return int
   */
  public function getTotalSteps()
  {
    return count($this->getSettings()->elements);
  }

  /**
   * @inheritDoc ITask::runStep()
   *
   * @param int $step
   *
   * @return bool
   */
  public function runStep($step)
  {
    // Again, bump the memory
    craft()->config->set('phpMaxMemoryLimit', '2560M');
    craft()->config->maxPowerCaptain();

    // Get the element we want to copy from
    $element = $this->getSettings()->elements[$step];

    // See if the one we are copying to already exists.
    // What you use to determine this will vary, in this case I just
    // used the title but you may need something more bullet proof.
    $criteria = craft()->elements->getCriteria(ElementType::Entry);
    $criteria->enabled   = null;
    $criteria->limit     = null;
    $criteria->status    = null;
    $criteria->sectionId = 22; // The ID of the section we are copying to
    $criteria->title     = $element->getContent()->title;
    $targetElement       = $criteria->first();

    // If we didn’t get an existing element, make one here
    if (!$targetElement) {
      $targetElement = new EntryModel();
      $targetElement->sectionId = 22;
      $targetElement->typeId    = 23;  // The ID of the Entry Type we want
    }

    // NOTE: This is where it gets fun - copy your field content!

    // Copy the blocks from a Matrix field - be aware that if the target
    // element already exists and has blocks they will be lost.
    // ref: https://craftcms.stackexchange.com/questions/8517/duplicating-matrix-fields-with-content-from-another-locale
    $newBlocks = array();
    $i = 0;

    foreach ($element->myMatrixField->find() as $block)
    {
      // Setup a new block
      $newBlock = new MatrixBlockModel();
      $newBlock->fieldId = 4; // Whatever the ID of `myMatrixField` is
      $newBlock->typeId  = $block->getType()->id;
      $newBlock->ownerId = $targetElement->id;
      $newBlock->locale  = $block->locale;

      $newBlockContent = $newBlock->getContent();

      $values = array();

      // Loop the fields on this block
      foreach ($block->getFieldLayout()->getFields() as $blockFieldLayoutField)
      {
        $field = $blockFieldLayoutField->getField();
        $fieldHandle = $field->handle;

        // Cope with element fields by getting an array of their IDs
        if (in_array($field->type, array('Assets', 'Entries', 'Categories', 'Tags'))) {
          $value = $block->$fieldHandle->ids();
        } else {
          // For ‘normal’ fields just copy their content directly
          $value = $block->$fieldHandle;
        }

        $values[$fieldHandle] = $value;
      }

      // Set the content on the new block
      $newBlock->setContentFromPost($values);

      $newBlocks['new'.$i] = $newBlock;
      $i++;
    }

    // Set the content on the target element
    $targetElement->setContent(array(
      
      // Don’t forget a title!
      'title' => $element->getContent()->title,
      
      // Here are the Matrix blocks we just made
      'myMatrixField' => $newBlocks,

      // Same as inside the Matrix, just get the IDs of relationship fields
      'someAssetField' => $element->someAssetField->ids(),

      // Simpler fields can just be directly copied
      'someSimpleTextField' => $element->someSimpleTextField,
    ));

  //  Keep a bunch of attributes
  $targetElement->setAttributes(array(
    'slug'          => $sourceElement->slug,
    'postDate'      => $sourceElement->postDate,
    'expiryDate'    => $sourceElement->expiryDate,
    'enabled'       => $sourceElement->enabled,
    'archived'      => $sourceElement->archived,
    'localeEnabled' => $sourceElement->localeEnabled,
  ));

    // Wrap in a transaction in case something goes wrong
    $transaction = craft()->db->getCurrentTransaction() === null ? craft()->db->beginTransaction() : null;
    try {

      // Try and save, throw an exception if it didn’t for some reason
      if (!craft()->entries->saveEntry($targetElement)) {

        // Try and get the errors so the log is more useful
        if ($targetElement->hasErrors()) {
          $firstError = array_shift($targetElement->getErrors())[0];
          throw new Exception(Craft::t('Couldn’t migrate from {title}. First error to correct: {error}', array('title' => $element->title, 'error' => firstError)));
        } else {
          throw new Exception(Craft::t('Couldn’t migrate from {title}.', array('title' => $element->title)));
        }        

      }

      if ($transaction !== null)
      {
        $transaction->commit();
      }

    } catch (Exception $e) {

      if ($transaction !== null)
      {
        $transaction->rollback();
      }

      // Log that exception message so we can debug it in the log viewer
      MyPlugin::log($e->getMessage(), LogLevel::Error);
      return $e->getMessage();

    }

    return true;

  }

  /**
   * @inheritDoc BaseSavableComponentType::defineSettings()
   *
   * @return array
   */
  protected function defineSettings()
  {

    return array(
      'elements' => AttributeType::Mixed
    );

  }

}

MyPluginController.php

<?php
namespace Craft;

class MyPluginController extends BaseController
{
  
  // This lets anyone run the controller actions we specify, useful for CRON etc
	protected $allowAnonymous = array('actionMigrate');
	
	/**
	 * Start the migration Task
   */
  public function actionMigrate()
  {
    // Create the Task
    craft()->tasks->createTask('MyPlugin_MigrateManager');

    if (!craft()->tasks->isTaskRunning()) {
      // Is there a pending task?
      $task = craft()->tasks->getNextPendingTask();

      if ($task) {
        // Attempt to close the connection if this is an Ajax request
        if (craft()->request->isAjaxRequest()) {
          craft()->request->close();
        }

        // Start running tasks
        craft()->tasks->runPendingTasks();
      }
    }
  }
  
}