Chapter 11: Migrating Existing PHP Apps to PHP 8

Throughout the book, you have been warned of potential code breaks. Unfortunately, there are not really any good tools available that can scan your existing code and check for potential code breaks. In this chapter, we take you through the development of a set of classes that form the basis of a PHP 8 backward-compatible (BC) break scanner. In addition, you learn the recommended process to migrate an existing customer PHP application to PHP 8.

After reading through this chapter and carefully studying the examples, you are much better equipped to handle a PHP 8 migration. With knowledge of the overall migration procedure, you gain confidence and are able to perform PHP 8 migrations with a minimal number of problems.

The topics covered in this chapter include the following:

• Understanding development, staging, and production environments
• Learning how to spot BC breaks before a migration
• Performing the migration
...

Technical requirements

To examine and run the code examples provided in this chapter, the minimum recommended hardware is the following:

• An x86_64-based desktop PC or laptop
• 1 gigabyte (GB) free disk space
• 4 GB of RAM
• 500 kilobits per second (Kbps) or faster internet connection

In addition, you will need to install the following software:

• Docker
• Docker Compose

Please refer to the Technical requirements section of Chapter 1, Introducing New PHP 8 OOP Features, for more information on Docker and Docker Compose installation, as well as how to build the Docker container used to demonstrate the code explained in this book. In this book, we refer to the directory in which you restored the sample code for this book as /repo.

The source code for this chapter is located at https://github.com/PacktPublishing/PHP-8-Programming-Tips-Tricks-and-Best-Practices. We can now begin our discussion by having a look at environments used as part of the overall...

Understanding development, staging, and production environments

The ultimate goal for a website update is to move the updated application code from development to production in as seamless a manner as possible. This movement of application code is referred to as deployment. Movement, in this context, involves copying application code and configuration files from one environment to another.

Before we get into the details of migrating an application to PHP 8, let's first have a look at what these environments are. Gaining an understanding of what form the different environments might take is critical to your role as a developer. With this understanding, you are in a better position to deploy your code to production with a minimal amount of errors.

Defining an environment

We use the word environment to describe a combination of software stacks that include the operating system, web server, database server, and PHP installation. In the past, the environment equated to a...

Learning how to spot BC breaks before a migration

Ideally, you should go into the PHP 8 migration with an action plan in hand. A critical part of this action plan includes getting an idea of how many potential BC breaks exist in your current code base. In this section, we show you how to develop a BC break sniffer that automates the process of looking through hundreds of code files for potential BC breaks.

First, we'll step back and review what we've learned so far about BC issues that might arise in PHP 8.

Gaining an overview of BC breaks

You already know, having read the previous chapters in this book, that potential code breaks originate from several sources. Let's briefly summarize the general trends that might lead to code failure after a migration. Please note that we do not cover these topics in this chapter as these are the topics that have all been covered in earlier chapters in this book:

• Resource-to-object migration
• Minimum versions for...

Performing the migration

Performing the actual migration from your current version to PHP version 8 is much like the process of deploying a new set of features to an existing application. If possible, you might consider running two websites in parallel until such time as you are confident the new version works as expected. Many organizations run the staging environment in parallel with the production environment for this purpose.

In this section, we present a twelve-step guide to perform a successful migration. Although we are focused on migrating to PHP 8, these twelve steps can apply to any PHP update you may wish to perform. Understanding and following these steps carefully is critical to the success of your production website. Included in the twelve steps are plenty of places where you can revert to an earlier version if you encounter problems.

Before we get into details, here is a general overview of a twelve-step migration process going from an older version of PHP to PHP...

Testing and troubleshooting the migration

In an ideal world, the migration troubleshooting will take place on the staging server, or simulated virtual environment, well before the actual move to production. However, as the seasoned developer well knows, we need to hope for the best, but prepare for the worst! In this section, we cover additional aspects of testing and troubleshooting that can be easily overlooked.

For the purposes of this section, you can exit the temporary shell if you were following the Debian/Ubuntu or the Red Hat/CentOS/Fedora installation process. Return to the Docker container used for this course and open a command shell into the PHP 8 container. Please refer to the Technical requirements section of Chapter 1, Introducing New PHP 8 OOP Features, for more information on how to do this if you are unsure.

Testing and troubleshooting tools

There are too many fine testing and troubleshooting tools available to document here, so we focus on a few open source...

Summary

In this chapter, you learned how the term environment is used rather than server because many websites these days use virtualized services. You then learned about three distinct environments used during the deployment phase: development, staging, and production.

An automated tool that is able to scan your application code for potential code breaks was introduced next. As you learned in that section, a break-scanning application might consist of a configuration file that addresses removed functionality, changes to method signatures, functions that no longer produce resources, and a set of callbacks for complex usage detection, a scanning class, and a calling program that gathers filenames.

Next, you were shown a typical twelve-step PHP 8 migration procedure that ensures a greater chance of success when you are finally ready to upgrade the production environment. Each step is designed to spot potential code breaks, with fallback procedures in case something goes wrong....