oliverdavies.uk/content/node.01893784-8f45-4466-8586-17df23e7e4b5.yml

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title:
  - value: "What's the correct way to add PHPStan to an existing codebase?"
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  - value: '2025-03-16T00:00:00+00:00'
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      <p>PHPStan is a static analysis tool for PHP.</p>

      <p>It finds potential issues in PHP code without needing to run it, so Developers can find and resolve potential issues sooner.</p>

      <p>I use it on all my projects including existing ones I've inherited.</p>

      <p>But how can you add a static analysis tool to a codebase without getting a lot of errors from the existing code?</p>

      <p>PHPStan has different levels of strictness.</p>

      <p>Level 0 is the least strict and each level adds more rules and strictness, resulting in more errors.</p>

      <p>Most of the time, people will start by running PHPStan on level 0, fixing any errors and committing the changes.</p>

      <p>Then repeat the process as many times as needed until you reach the level you want to achieve.</p>

      <p>I don't think this is the right approach.</p>

      <p>This could mean that you need to edit the same files multiple times as you work through the levels.</p>

      <p>There's also a period of time where Developers can still write suboptimal code whilst you work your way up to your desired level.</p>

      <p>Another approach is to use a feature of PHPStan called the baseline.</p>

      <p>The baseline is a way of capturing and saving all the existing errors up to the selected level so they are no longer reported.</p>

      <p>If you did this for an existing project, it would return no errors as everything would be included in the baseline.</p>

      <p>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.</p>

      <p>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.</p>

      <p>This I think is a better approach and how I add PHPStan to existing codebases.</p>

      <p>To learn more about static analysis and PHPStan, listen to <a href="/podcast/22-dave-liddament">episode 22 of the Beyond Blocks podcast</a> with Dave Liddament.</p>

              
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      <p>PHPStan is a static analysis tool for PHP.</p>

      <p>It finds potential issues in PHP code without needing to run it, so Developers can find and resolve potential issues sooner.</p>

      <p>I use it on all my projects including existing ones I've inherited.</p>

      <p>But how can you add a static analysis tool to a codebase without getting a lot of errors from the existing code?</p>

      <p>PHPStan has different levels of strictness.</p>

      <p>Level 0 is the least strict and each level adds more rules and strictness, resulting in more errors.</p>

      <p>Most of the time, people will start by running PHPStan on level 0, fixing any errors and committing the changes.</p>

      <p>Then repeat the process as many times as needed until you reach the level you want to achieve.</p>

      <p>I don't think this is the right approach.</p>

      <p>This could mean that you need to edit the same files multiple times as you work through the levels.</p>

      <p>There's also a period of time where Developers can still write suboptimal code whilst you work your way up to your desired level.</p>

      <p>Another approach is to use a feature of PHPStan called the baseline.</p>

      <p>The baseline is a way of capturing and saving all the existing errors up to the selected level so they are no longer reported.</p>

      <p>If you did this for an existing project, it would return no errors as everything would be included in the baseline.</p>

      <p>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.</p>

      <p>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.</p>

      <p>This I think is a better approach and how I add PHPStan to existing codebases.</p>

      <p>To learn more about static analysis and PHPStan, listen to <a href="/podcast/22-dave-liddament">episode 22 of the Beyond Blocks podcast</a> with Dave Liddament.</p>

              
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