How to debug PHP function type errors with PHPStan?

Use PHPStan to debug type errors in PHP functions: Use PHPStan to analyze code to infer the types of variables and check that these types are as expected. Use PHPStan by installing it, configuring profiles, and running analysis commands. Common errors include type hint mismatch, return value type mismatch, and untyped variables. Through PHPStan's reports, these errors can be easily identified and fixed to ensure the correctness and robustness of your code.

How to use PHPStan to debug type errors in PHP functions

PHPStan is a static analysis tool that can help you catch type errors in PHP code errors, including type errors. It analyzes your code to infer the types of variables and checks whether they match the expected types.

Install PHPStan

To install PHPStan, run the following command in the terminal:

composer global require phpstan/phpstan

Configure PHPStan

Next, create a phpstan.neon configuration file and place it in your project root directory. In this configuration file, you can specify the directories to be analyzed, the inspection level, and other options. For example:

parameters:
  level: max
  paths:
    - src

Run PHPStan

To run PHPStan, run the following command in the terminal:

phpstan analyse

Read the report

PHPStan will generate a report containing detected errors and warnings. Common messages for locating type errors include:

• Type hint mismatch: When the types of the actual parameters of a function do not match the hint types in the function declaration.
• Return value type mismatch: When the actual type returned by a function does not match the declared return type.
• Untyped variable: When the variable used by the function does not have a type hint.

Practical case

Consider the following example function:

function addNumbers(int $a, int $b): int
{
    return $a + $b;
}

addNumbers('a', 'b');

If we run PHPStan, it will output the following error:

Parameter #1 $a of addNumbers() expects int, string given.
Parameter #2 $b of addNumbers() expects int, string given.

Fix type errors

To fix these errors we need to type-cast the parameters passed to addNumbers to integers:

addNumbers((int)'a', (int)'b');

Conclusion

By using PHPStan, you can easily detect and fix type errors in PHP functions. By analyzing your code and inferring variable types, PHPStan can help you ensure that your code is correct and robust.

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