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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| 8 | class ArticleController extends Controller  | 
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| 9 | { | 
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| 10 | public function __construct()  | 
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| 16 | |||
| 17 | /**  | 
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| 18 | * Show the list of all articles.  | 
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| 19 | *  | 
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| 20 | * @return \Illuminate\Http\Response  | 
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| 21 | */  | 
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| 22 | public function index()  | 
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| 29 | |||
| 30 | /**  | 
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| 31 | * Show the article by his id.  | 
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| 32 | *  | 
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| 33 | * @return \Illuminate\Http\Response  | 
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| 34 | */  | 
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| 35 | View Code Duplication | public function show(Request $request, $slug, $id)  | 
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| 62 | }  | 
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| 63 | 
In PHP it is possible to write to properties without declaring them. For example, the following is perfectly valid PHP code:
Generally, it is a good practice to explictly declare properties to avoid accidental typos and provide IDE auto-completion: