Drupal 11

This is the third article in a series of articles about the Batch API in Drupal. The Batch API is a system in Drupal that allows data to be processed in small chunks in order to prevent timeout errors or memory problems.

So far in this series we have looked at creating a batch process using a form and then creating a batch class so that batches can be run through Drush. Both of these examples used the Batch API to run a set number of items through a set number of process function callbacks. When setting up the batch run we created a list of items that we wanted to process and then split this list up into chunks, each chunk being sent to a batch process callback.

There is another way to set up the Batch API that will run the same number of operations without defining how many times we want to run them first. This is possible by using the "finished" setting in the batch context.

This is the second part of a series of articles looking at the Batch API in Drupal. The Batch API is a system in Drupal that allows data to be processed in small chunks in order to prevent timeout errors or memory problems.

In the previous article we looked at how to setup the batch process using a form, with the batch methods being contained within the structure of the form class. When the form was submitted the batch process ran through 1,000 items and then printed out a result at the end.

Whilst there is nothing wrong with running the Batch API with everything in a form class, it is normally better to abstract the batch processing code into a separate class.

The Batch API is a powerful feature in Drupal that allows complex or time consuming tasks to be split into smaller parts.

For example, let's say you wanted to run a function that would go through every page on you Drupal site and perform an action. This might be removing specific authors or removing links in text. You might create a small loop that just loads all pages and performs the action on those pages.

This is normally fine on sites that have a small number of pages, like under 100 pages. But what happens when the site has 10,000 pages, or a million? Your little loop will soon hit the limits of PHP execution times or memory limits and cause the page to be terminated. How do you know how far your loop progressed through the data? What happens if you tried to restart the loop?