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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10 | final class TokenContainer implements Cleanable, ContainsChildren, Removable |
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11 | { |
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12 | /** @var array[Token] */ |
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13 | private $children; |
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14 | |||
15 | /** @var Configuration */ |
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16 | private $configuration; |
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17 | |||
18 | /** |
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19 | * Constructor |
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20 | */ |
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21 | 51 | public function __construct(Configuration $configuration) |
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26 | |||
27 | /** |
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28 | * Required by ContainsChildren interface. |
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29 | */ |
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30 | 51 | public function getChildren() |
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34 | |||
35 | /** |
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36 | * Required by ContainsChildren interface. |
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37 | */ |
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38 | 1 | public function hasChild(Token $token) |
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42 | |||
43 | /** |
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44 | * Required by ContainsChildren interface. |
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45 | */ |
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46 | 50 | public function appendChild(Token $token) |
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52 | |||
53 | /** |
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54 | * Required by ContainsChildren interface. |
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55 | */ |
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56 | 1 | public function prependChild(Token $token) |
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62 | |||
63 | /** |
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64 | * Required by ContainsChildren interface. |
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65 | */ |
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66 | 5 | View Code Duplication | public function removeChild(Token $token) |
77 | |||
78 | /** |
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79 | * Required by Cleanable interface. |
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80 | */ |
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81 | 43 | public function clean(LoggerInterface $logger) |
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89 | |||
90 | /** |
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91 | * Required by the Removable interface. |
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92 | */ |
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93 | 42 | View Code Duplication | public function remove(LoggerInterface $logger) |
123 | } |
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124 |
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: