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:
| 1 | <?php | ||
| 8 | View Code Duplication | class CheckerIsStillFailing extends CheckerHasFailed | |
| 9 | { | ||
| 10 | /** | ||
| 11 | * The checker. | ||
| 12 | * | ||
| 13 | * @var \ProtoneMedia\ApiHealth\Checkers\Checker | ||
| 14 | */ | ||
| 15 | public $checker; | ||
| 16 | |||
| 17 | /** | ||
| 18 | * The exception. | ||
| 19 | * | ||
| 20 | * @var \ProtoneMedia\ApiHealth\Checkers\CheckerHasFailed | ||
| 21 | */ | ||
| 22 | public $exception; | ||
| 23 | |||
| 24 | /** | ||
| 25 | * The failed data. | ||
| 26 | * | ||
| 27 | * @var array | ||
| 28 | */ | ||
| 29 | public $failedData; | ||
| 30 | |||
| 31 | /** | ||
| 32 | * Creates a new instance of this event. | ||
| 33 | * | ||
| 34 | * @param \ProtoneMedia\ApiHealth\Checkers\Checker $checker | ||
| 35 | * @param \ProtoneMedia\ApiHealth\Checkers\CheckerHasFailed $exception | ||
| 36 | * @param array $failedData | ||
| 37 | */ | ||
| 38 | public function __construct(Checker $checker, CheckerHasFailed $exception, array $failedData) | ||
| 44 | } | ||
| 45 | 
Let’s assume that you have a directory layout like this:
. |-- OtherDir | |-- Bar.php | `-- Foo.php `-- SomeDir `-- Foo.phpand let’s assume the following content of
Bar.php:If both files
OtherDir/Foo.phpandSomeDir/Foo.phpare loaded in the same runtime, you will see a PHP error such as the following:PHP Fatal error: Cannot use SomeDir\Foo as Foo because the name is already in use in OtherDir/Foo.phpHowever, as
OtherDir/Foo.phpdoes not necessarily have to be loaded and the error is only triggered if it is loaded beforeOtherDir/Bar.php, this problem might go unnoticed for a while. In order to prevent this error from surfacing, you must import the namespace with a different alias: