What Happens Under the Hood

Oct 13, 2025 by leolavanderia.com.br 99 views

Understanding PHPStan's Limitations

PHPStan is a static analysis tool that helps developers catch errors and improve code quality. However, like any tool, it has its limitations. In this article, we will explore a specific issue where PHPStan fails to report a call to an undefined method when the method call overwrites the variable holding the object.

The Problem

The problem arises when a method is called on an object that does not exist. PHPStan does not detect this issue if the call is performed inside a loop and the method call overwrites the variable holding the object. This can lead to unexpected behavior and errors.

Example Code

Let's consider an example code snippet that demonstrates this issue:

function (MyObj $obj) {
    while (1) {
        $obj = $obj->iDoNotExist();
    }
};

In this example, the method iDoNotExist() is called on the object $obj. However, this method does not exist, and PHPStan does not report this issue.

What Happens Under the Hood

When PHPStan analyzes the code, it infers the type of the variable $obj to be MyObj. However, when the method iDoNotExist() is called, the type of $obj changes to mixed. This is because the method call overwrites the variable holding the object, and PHPStan cannot infer the correct type.

Expected Output

The expected output from PHPStan should be:

> 5: Call to an undefined method DateTimeInterface::add().

However, since the type of $obj is inferred to be mixed, PHPStan does not report this issue.

Feature Request

This issue could be considered a feature request for PHPStan. It would be beneficial for PHPStan to understand that on the first iteration, $obj is MyObj, and report that the method does not exist.

Code Snippet that Reproduces the Problem

The code snippet that reproduces this problem can be found at: https://phpstan.org/r/2c43e149-e1f8-4e6f-957c-6fdaecd337d6

Conclusion

In conclusion, PHPStan has limitations when it comes to detecting calls to undefined methods. This issue arises when the method call overwrites the variable holding the object, and the type of the variable changes to mixed. While this is not a critical issue, it is still a limitation that developers should be aware of.

PHPStan and Code Quality

PHPStan is a powerful tool that helps developers catch errors and improve code quality. While it has its limitations, it is still an essential tool for any PHP developer. By using PHPStan, developers can ensure that their code is of high quality and free from errors.

PHPStan and Happiness

The final question is: did PHPStan help you today? Did it make you happy in any way? For many developers, PHPStan is a daily companion that helps them catch errors and improve their code. While it may not make them happy in the classical sense, it certainly helps them write better code.

Conclusion

In conclusion, PHPStan is a powerful tool that helps developers catch errors and improve code quality. While it has its limitations, it is still an essential tool for any PHP developer. By using PHPStan, developers can ensure that their code is of high quality and free from errors.

Recommendations

Use PHPStan to catch errors and improve code quality.
Be aware of the limitations of PHPStan, including the issue discussed in this article.
Consider reporting feature requests to the PHPStan team to improve the tool.

Final Thoughts

Q&A: Understanding PHPStan's Limitations

In our previous article, we explored a specific issue where PHPStan fails to report a call to an undefined method when the method call overwrites the variable holding the object. In this article, we will answer some frequently asked questions related to this issue.

Q: What is the issue with PHPStan not reporting a call to an undefined method?

A: The issue arises when a method is called on an object that does not exist. PHPStan does not detect this issue if the call is performed inside a loop and the method call overwrites the variable holding the object.

Q: What happens under the hood when PHPStan analyzes the code?

A: When PHPStan analyzes the code, it infers the type of the variable to be MyObj. However, when the method is called, the type of the variable changes to mixed because the method call overwrites the variable holding the object.

Q: Why does PHPStan not report the issue when the type of the variable is `mixed`?

A: PHPStan does not report the issue when the type of the variable is mixed because it cannot infer the correct type of the variable. In this case, the variable is treated as a generic type, and PHPStan does not report the issue.

Q: Is this a critical issue?

A: No, this is not a critical issue. However, it is still a limitation that developers should be aware of.

Q: Can I report this issue to the PHPStan team?

A: Yes, you can report this issue to the PHPStan team as a feature request. This will help the team to improve the tool and make it more robust.

Q: How can I prevent this issue in my code?

A: To prevent this issue in your code, you can avoid using loops that overwrite the variable holding the object. Alternatively, you can use a different approach to call the method, such as using a separate variable to hold the object.

Q: What are the benefits of using PHPStan?

A: The benefits of using PHPStan include:

Improved code quality
Reduced errors
Better maintainability
Improved performance

Q: Can I use PHPStan with other tools?

A: Yes, you can use PHPStan with other tools, such as PHP CodeSniffer and PHPMD. PHPStan can be integrated with these tools to provide a more comprehensive analysis of your code.

Q: How can I get started with PHPStan?

A: To get started with PHPStan, you can follow these steps:

Install PHPStan using Composer.
Configure PHPStan to analyze your code.
Run PHPStan to analyze your code.
Review the results and fix any issues.

Conclusion

Recommendations

Use PHPStan to catch errors and improve code quality.
Be aware of the limitations of PHPStan, including the issue discussed in this article.
Consider reporting feature requests to the PHPStan team to improve the tool.