# Mezzio Example: Psalm Introduction

## What is Psalm?

Psalm is a static analysis tool for PHP that helps you identify problems with your code. If you use it, you’ll become a better coder. I promise.

Here’s a great read – the story of the origins of Psalm at Vimeo and the value it provided the team.

https://psalm.dev/articles/fixing-code-that-aint-broken

In this post, I’ll show a basic setup for static analysis with Psalm in Mezzio applications.

## Configuration

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## Changes Required for Psalm Error Level 1

It’s probably easiest to read the diff here:

https://github.com/marcguyer/mezzio-doctrine-oauth2-example/commit/b1b781a85eeef46c4f7168ea0670219dd40753af

## What’s Next?

The next post in this series adds Doctrine Entity classes and tests. We’ll create only those models necessary for a baseline OAuth2 implementation.

#### Series: Mezzio Example

1. Mezzio Example: Introduction
2. Mezzio Example: Functional and Unit Testing
3. Mezzio Example: Psalm Introduction
4. Mezzio Example: Doctrine Entities and Repositories