Documentation Strategy During PHP Upgrades

In the early 1900s, constructing the Panama Canal was one of humanity’s most ambitious engineering projects. Workers faced tropical diseases, unpredictable weather, and massive earth-moving operations. The project’s success hinged not just on machinery but on meticulous documentation—daily logs, engineering diagrams, and progress reports that allowed teams to coordinate across thousands of workers and make decisions based on accurate information.

A PHP upgrade may seem less monumental, but the parallels are striking. You’re managing a complex system with many interdependent parts, facing potential pitfalls that can derail your progress, and coordinating with team members who need clear guidance. We are not just talking about writing essays; we’re talking about creating a reliable record that keeps your upgrade on track.

That’s why a robust documentation strategy is your most powerful upgrade tool. It transforms the process from a risky gamble into a predictable, manageable task. This post outlines a practical, three-phase approach to documenting your PHP upgrade process, turning chaos into a well-lit path.

Why Documentation Transforms Upgrades from Risky Ventures to Predictable Processes

Before diving into the “how,” let’s establish the “why.” A clear documentation strategy transforms your upgrade approach from reactive problem-solving to proactive, structured execution. Documentation serves as:

• A Single Source of Truth: Eliminates ambiguity and ensures every team member works from the same playbook.
• A Risk Reduction Mechanism: By auditing your application and planning the upgrade path, you identify potential pitfalls before they become production issues.
• A Reusable Playbook: Future upgrades become faster and more predictable because we aren’t starting from scratch each time.
• A Knowledge Transfer Tool: Onboarding new developers or transitioning responsibilities becomes seamless when the application’s history and state are clearly documented.

One may wonder: why do we need all this documentation? Can’t we just upgrade and fix issues as they arise? The answer is straightforward: documentation turns reactive firefighting into a systematic, repeatable process. Without it, you are relying on memory and ad-hoc decisions, which increases risk and makes future upgrades harder.

With this foundation established, let’s examine the three-phase approach in detail. We’ll start with pre-upgrade documentation, which forms the blueprint for your entire upgrade process.

Phase 1: Pre-Upgrade Documentation (The Blueprint)

This is the most critical phase. The documentation you create here forms the foundation for the entire project. Rushing this step is a common cause of upgrade failures.

1. The Current State Audit

You can’t map out a journey without knowing your starting point. Document the exact state of your production environment:

• PHP Version: php -v (include patch version and distro). For example:

  $ php -v
  PHP 8.1.20 (cli) (built: Oct 31 2024 15:12:17) ...

  Note that the patch version (the third number) matters—security fixes are often backported to specific patch releases, so documenting the exact version prevents ambiguity.
• PHP Extensions: php -m (list all compiled and enabled extensions). Save the full output to a file: php -m > php-extensions.txt.
• Composer Dependencies: composer show (capture exact versions of all packages). For example, in a Laravel 10.10.0 application using Guzzle 7.8.2 and PHPStan 1.10.35, you would see output like:

  $ composer show | head -20
  name     : laravel/framework
  versions : * 10.10.0
  descrip. : The Laravel Framework.
  name     : guzzlehttp/guzzle
  versions : * 7.8.2
  ...

• Server Environment: OS version (cat /etc/os-release), web server (Nginx/Apache) version, database versions, and any other critical services (Redis, Elasticsearch, etc.).

Tip: Create a standardized template for this audit information. Save it as docs/current-state-audit-template.md in your repository with placeholders like [PHP_VERSION], [UBUNTU_VERSION], [NGINX_VERSION]. This ensures consistency across team members and makes the audit process repeatable for future upgrades.

We recommend creating a standardized template for this information.

• Environment Variables: A list of all .env keys required to run the application. You can generate this by checking your codebase for getenv() calls, or by documenting from your production environment. Though it’s tempting to skip this, we’ve found it’s better to be comprehensive.

2. Deprecation and Change Analysis

With your target PHP version in mind, we create a document that lists all deprecated functions, classes, and features currently used in your codebase. Tools like PHPStan 1.10+ with the phpstan-deprecation-rules extension can automate much of this discovery. For instance, after installing PHPStan:

$ vendor/bin/phpstan analyse app/ --level=max
...
 ------ --------------------------------------------------------------
  Line   app/Controllers/UserController.php
 ------ --------------------------------------------------------------
  42     Call to deprecated function each(). Deprecated since PHP 7.2.
  108    Function create_function() is deprecated.
 ------ --------------------------------------------------------------

Though the output format may vary slightly depending on your configuration, the key is identifying each occurrence.

For each deprecated item, document:

• The deprecated function/feature (e.g., each(), create_function()).
• The file and line number where it’s used.
• The recommended replacement (e.g., foreach for each(), anonymous functions for create_function()).
• An estimate of the effort required to refactor using specific timeframes: low (under 2 hours), medium (2-8 hours), high (1+ days). This granularity helps prioritize work during the upgrade.

3. The Upgrade Checklist and Plan

This document is your step-by-step guide. It should be clear enough for any developer on your team to follow. Use a format like a Markdown checklist. We recommend including specific commands and version numbers relevant to your project. For example, if you are upgrading from PHP 8.1 to 8.2:

- [ ] **Pre-Upgrade Steps**
  - [ ] Backup production database (`mysqldump -u user -p dbname > backup.sql`) and file storage (`rsync -avz /var/www/storage/ /backup/storage/`).
  - [ ] Announce code freeze to the development team in Slack #dev-channel.
  - [ ] Run final test suite on the current branch: `./vendor/bin/phpunit` to confirm it's green.
  - [ ] Commit any pending changes and tag current release: `git tag -a v1.2.3 -m "Pre-upgrade snapshot"`.
- [ ] **Upgrade Execution**
  - [ ] Create a new `upgrade/php-8.2` branch: `git checkout -b upgrade/php-8.2`.
  - [ ] Update `composer.json` to require `"php": "^8.2"` instead of `"^8.1"`.
  - [ ] **Safety reminder:** Before running `composer update`, ensure **you** have a clean working tree and recent commit. This command will modify many dependencies.
  - [ ] Run `composer update` with the `--no-dev` flag for production: `composer update --no-dev --optimize-autoloader`.
  - [ ] Run `composer update` on staging/local environment first to catch issues early.
- [ ] **Post-Upgrade Steps**
  - [ ] Deploy to the staging environment: `git push origin upgrade/php-8.2 && cap staging deploy`.
  - [ ] Perform QA and user acceptance testing (UAT). Check all critical user journeys.
  - [ ] Run full test suite on staging: `./vendor/bin/phpunit --coverage`.
  - [ ] Schedule production deployment during low-traffic window (e.g., Sunday 2 AM EST).
  - [ ] Deploy to production and monitor logs for 24 hours: `tail -f /var/log/nginx/error.log`.

Tip: Keep your upgrade checklist as a Markdown file in your repository (e.g., docs/upgrade-checklist.md). This ensures it’s versioned alongside your code, appears in pull requests for team review, and persists even if your issue tracker changes. Tag it with the PHP version, like upgrade-php-8.2-checklist.md, for easy reference in future upgrades.

Though this example is specific to a Laravel application, you can adapt it to your framework and tooling. The key is being explicit about what commands to run and in what order.

Phase 2: During-Upgrade Documentation (The Logbook)

As the upgrade proceeds, documentation becomes a real-time log of your journey. We find this is not about writing essays; it’s about recording critical facts while they’re fresh in your mind.

The Issues & Resolutions Log

We recommend maintaining either a simple UPGRADE_LOG.md file in your repository or a dedicated Confluence page. For every unexpected issue, no matter how small, log it in this format:

**Date:** 2026-03-15

**Problem:** Composer conflict with "monolog/monolog" when running `composer update`.
Error: "Your requirements could not be resolved to an installable set of packages."

**Investigation:**
1. Ran `composer why-not monolog/monolog` to identify conflicts.
2. Discovered that `laravel/framework` required `^2.0` but **our** code used features from `^3.0`.
3. Checked GitHub issues: https://github.com/laravel/framework/issues/12345 suggested updating to Laravel 10.

**Solution:** Updated `composer.json` to require `"laravel/framework": "^10.0"` and resolved deprecated API calls in `app/Http/Controllers/LogController.php`. Commit: `abc123def`.

**Time spent:** 3 hours

Of course, you may not encounter every issue, but capturing them as they happen creates an invaluable resource for troubleshooting similar issues in the future and helps justify the time spent on the upgrade during retrospectives.

Phase 3: Post-Upgrade Documentation (The New Standard)

Once the upgrade is complete and deployed, a final round of documentation solidifies the new state of the application. We cannot stress enough how important this phase is for long-term maintainability.

1. The Final State Report

Create an updated version of your “Current State Audit” that reflects the new production environment. This becomes your new baseline for future upgrades. Make sure to capture:

• The new PHP version (e.g., PHP 8.2.12).
• Any new PHP extensions that were added.
• Updated Composer dependencies with their exact versions.
• Any new environment variables that were introduced during the upgrade.

2. Update Your “Runbooks”

Your developer onboarding and local environment setup guides are now outdated. You should update them immediately with the new requirements (e.g., required PHP version 8.2+, new environment variables like APP_KEY, updated setup commands such as composer install --no-dev). Though this might seem like extra work, we’ve found it pays off quickly when new developers join the team or when you need to rebuild environments.

3. The Knowledge Base Update

Summarize the key learnings from the “Issues & Resolutions Log” and share them with the entire engineering team. We recommend creating a concise page in your internal knowledge base (like Confluence, Notion, or a simple markdown file in a docs/ folder) that covers:

• A brief overview of the upgrade process—what PHP version you moved from and to, roughly how long it took, and what major changes were involved.
• The most significant challenges encountered and how you overcame them.
• Key architectural changes that were made (e.g., replaced each() with foreach, moved from monolog v1 to v3).
• A link to the full upgrade plan and issue log for future reference.

Of course, this documentation isn’t just for your team—it’s also valuable for anyone you might hire in the future, or for your future self when upgrading again in 2-3 years.

A Note on Alternatives

Of course, the three-phase documentation strategy presented here is not the only way to handle PHP upgrades. There are three common approaches teams use, each with distinct trade-offs and philosophical underpinnings.

Repository Markdown Files (the approach presented here) keep documentation version-controlled alongside your code. This creates a single source of truth that evolves with your application. The philosophy here is that documentation is part of the codebase—it should be reviewed in pull requests, tracked in git history, and remain available even if external services change. The downside is less robust workflow integration; you can’t assign tasks or track progress through a dedicated issue board.

Dedicated Issue Trackers like Jira or GitHub Issues treat each documentation item as a trackable task. This works well when documentation is a shared responsibility across many team members, or when you need fine-grained assignment and status tracking. The philosophy is that documentation work should be visible in the same way feature work is. The trade-off is that documentation becomes disconnected from specific code versions—you might have an issue #12345 describing a PHP 8.2 upgrade plan, but that issue doesn’t automatically update when you cherry-pick commits to a maintenance branch.

Internal Wikis (Confluence, Notion, etc.) provide centralized knowledge that spans multiple projects. They excel at creating organizational playbooks that apply across teams. The philosophy is that documentation should outlive any single repository and be easily discoverable by anyone in the organization. The trade-off is that wikis don’t have built-in version history tied to code releases, and it’s easy for documentation to drift from reality when updates happen in code but not in the wiki.

We personally prefer repository markdown files because they maintain traceability and accuracy over time. That said, many teams successfully combine approaches—for instance, keeping detailed upgrade checklists in markdown files while using issues to track progress, or linking to relevant wiki pages for organization-wide standards. Choose the approach that fits your team’s existing workflows, but whatever you choose, ensure documentation has a clear owner and update process. Without that, even the best-designed system will decay.

Conclusion

Treating documentation as an integral part of the PHP upgrade process transforms it from a dreaded, high-risk event into a predictable, value-adding engineering task. By creating a blueprint, keeping a logbook, and updating your standards, you not only ensure a successful upgrade but also pay down technical debt and make your application more resilient for the future. Of course, we recognize that adopting this three-phase approach requires discipline—though in our experience, the time invested upfront saves countless hours of debugging and firefighting later.

Start small. We recommend creating your first “Current State Audit” today. It’s the first step toward a smoother upgrade tomorrow—and a more maintainable codebase for years to come.