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 |
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11 | View Code Duplication | class Guilds |
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12 | { |
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13 | use ImmutableTrait, SerializableTrait; |
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14 | |||
15 | /** |
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16 | * @var string |
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17 | */ |
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18 | private $world; |
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19 | |||
20 | /** |
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21 | * @var Collection |
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22 | */ |
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23 | private $active; |
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24 | |||
25 | /** |
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26 | * @var Collection |
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27 | */ |
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28 | private $formation; |
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29 | |||
30 | /** |
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31 | * Guilds constructor. |
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32 | * @param string $world |
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33 | * @param array $active |
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34 | * @param array $formation |
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35 | * @throws ImmutableException |
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36 | */ |
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37 | public function __construct(string $world, Collection $active, Collection $formation) |
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45 | |||
46 | /** |
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47 | * @return string |
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48 | */ |
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49 | public function getWorld(): string |
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53 | |||
54 | /** |
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55 | * @return Guild[] |
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56 | */ |
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57 | public function getActive(): Collection |
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61 | |||
62 | /** |
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63 | * @return Guild[] |
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64 | */ |
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65 | public function getFormation(): Collection |
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69 | } |
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70 |
Let’s assume that you have a directory layout like this:
and let’s assume the following content of
Bar.php
:If both files
OtherDir/Foo.php
andSomeDir/Foo.php
are 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.php
However, as
OtherDir/Foo.php
does 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: