Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is
duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
interfaceUser{/** @return string */publicfunctiongetPassword();}classMyUserimplementsUser{publicfunctiongetPassword(){// return something}publicfunctiongetDisplayName(){// return some name.}}classAuthSystem{publicfunctionauthenticate(User$user){$this->logger->info(sprintf('Authenticating %s.',$user->getDisplayName()));// do something.}}
In the above example, the authenticate() method works fine as long as you just pass
instances of MyUser. However, if you now also want to pass a different implementation
of User which does not have a getDisplayName() method, the code will break.
classAuthSystem{publicfunctionauthenticate(User$user){if($userinstanceofMyUser){$this->logger->info(/** ... */);}// or alternativelyif(!$userinstanceofMyUser){thrownew\LogicException('$user must be an instance of MyUser, '.'other instances are not supported.');}}}
Note: PHP Analyzer uses reverse abstract interpretation to narrow down the types
inside the if block in such a case.
This code seems to be duplicated across your project.
Duplicated code is one of the most pungent code smells. If you need to duplicate
the same code in three or more different places, we strongly encourage you to
look into extracting the code into a single class or operation.
You can also find more detailed suggestions in the “Code” section of your repository.
Let’s take a look at an example:
In the above example, the authenticate() method works fine as long as you just pass instances of MyUser. However, if you now also want to pass a different implementation of User which does not have a getDisplayName() method, the code will break.
Available Fixes
Change the type-hint for the parameter:
Add an additional type-check:
Add the method to the interface: