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Cognitive complexity tells us, how difficult code is to understand by a reader.

How is cognitive complexity measured?

functionget_words_from_number(int$number):string{$amountInWords ='';if ($number ===1) {// + 1$amountInWords ='one';    }elseif ($number ===2) {// + 1$amountInWords ='couple';    }elseif ($number ===3) {// + 1$amountInWords ='a few';    }else {// + 1$amountInWords ='a lot';    }return$amountInWords;}

This function uses nesting, conditions and continue back and forth. It's hard to read and results incognitive complexity of 4.

How to keepcognitive complexity on 1? ReadCognitive load is what matters orSonar paper about cognitive complexity metrics that inspired this repository.

composer require tomasvotruba/cognitive-complexity --dev

The package is available on PHP 7.4+.

WithPHPStan extension installer, everything is ready to run.

Enable each item on their own with simple configuration:

# phpstan.neonparameters:cognitive_complexity:class:50function:8

In classes like controllers, Rector rules, PHPStan rules or other services of specific type, the complexity can be hidden in the __construct() dependencies. Simple class with 10 dependencies is more complex than complex class with 2 dependencies.

That's why there is a rule to detect these dependency trees. It checks:

• complexity ofcurrent class
• constructor dependencies and their class complexity together

Final number is compared and used as a final complexity:

# phpstan.neonparameters:cognitive_complexity:dependency_tree:150dependency_tree_types:# only these explicit types are checked, nothing else            -Rector\Contract\Rector\RectorInterface

Happy coding!