Add daily email for 2025-03-16

What's the correct way to add PHPStan to an existing codebase?

source/_daily_emails/2025-03-16.md

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+---
+title: What's the correct way to add PHPStan to an existing codebase?
+date: 2025-03-16
+permalink: daily/2025/03/16/what-s-the-correct-way-to-add-phpstan-to-an-existing-codebase
+tags:
+  - software-development
+  - php
+  - phpstan
+  - static-analysis
+cta: ~
+snippet: |
+  What's the correct way to add PHPStan to an existing codebase?
+---
+
+PHPStan is a static analysis tool for PHP.
+
+It finds potential issues in PHP code without needing to run it, so Developers can find and resolve potential issues sooner.
+
+I use it on all my projects including existing ones I've inherited.
+
+But how can you add a static analysis tool to a codebase without getting a lot of errors from the existing code?
+
+PHPStan has different levels of strictness.
+
+Level 0 is the least strict and each level adds more rules and strictness, resulting in more errors.
+
+Most of the time, people will start by running PHPStan on level 0, fixing any errors and committing the changes.
+
+Then repeat the process as many times as needed until you reach the level you want to achieve.
+
+I don't think this is the right approach.
+
+This could mean that you need to edit the same files multiple times as you work through the levels.
+
+There's also a period of time where Developers can still write suboptimal code whilst you work your way up to your desired level.
+
+Another approach is to use a feature of PHPStan called the baseline.
+
+The baseline is a way of capturing and saving all the existing errors up to the selected level so they are no longer reported.
+
+If you did this for an existing project, it would return no errors as everything would be included in the baseline.
+
+Once you decide what level you want your project to run, you can start as soon as the baseline is generated and without needing to change files multiple times.
+
+Instead of spending time working through the levels one at a time, commit some time to pruning the baseline and reducing the errors in it.
+
+This I think is a better approach and how I add PHPStan to existing codebases.
+
+To learn more about static analysis and PHPStan, listen to [episode 22 of the Beyond Blocks podcast][0] with Dave Liddament.
+
+[0]: {{site.url}}/podcast/22-dave-liddament