If you want to use PHPStan but your codebase isn’t up to speed with strong typing and PHPStan’s strict checks, you can currently choose from 10 levels (0 is the loosest and 9 is the strictest) by passing
-l|--level to the
vendor/bin/phpstan analyse -l 6 src tests
The default level is 0. Once you specify a configuration file, you also have to specify the level to run.
This feature enables incremental adoption of PHPStan checks. You can start using PHPStan with a lower rule level and increase it when you feel like it.
To be able to run a higher level without fixing all the reported errors first, check out a feature called the baseline.
You can also use
--level max as an alias for the highest level. This will ensure that you will always use the highest level when upgrading to new versions of PHPStan. 
Here’s a brief overview of what’s checked on each level. Levels are cumulative - for example running level 5 also gives you all the checks from levels 0-4.
- basic checks, unknown classes, unknown functions, unknown methods called on
$this, wrong number of arguments passed to those methods and functions, always undefined variables
- possibly undefined variables, unknown magic methods and properties on classes with
- unknown methods checked on all expressions (not just
$this), validating PHPDocs
- return types, types assigned to properties
- basic dead code checking - always false
instanceofand other type checks, dead
elsebranches, unreachable code after return; etc.
- checking types of arguments passed to methods and functions
- report missing typehints
- report partially wrong union types - if you call a method that only exists on some types in a union type, level 7 starts to report that; other possibly incorrect situations
- report calling methods and accessing properties on nullable types
- be strict about the
mixedtype - the only allowed operation you can do with it is to pass it to another
Please note that this can create a significant obstacle when upgrading to a newer version because you might have to fix a lot of code to bring the number of errors down to zero. ↩︎