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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| 12 | class VKUsers extends VKAPI { | 
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| 13 | |||
| 14 | /**  | 
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| 15 | * API Method for this class  | 
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| 16 | * @var string  | 
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| 17 | */  | 
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| 18 | protected $apiMethod = 'users.';  | 
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| 19 | |||
| 20 | /**  | 
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| 21 | * Default Fields For Selection  | 
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| 22 | */  | 
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| 23 | const standardFields = [ 'sex', 'online', 'country', 'city', 'bdate' ];  | 
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| 24 | |||
| 25 | /**  | 
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| 26 | * VKUsers constructor.  | 
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| 27 | * @param VKBase $vkObject  | 
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| 28 | */  | 
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| 29 |     public function __construct(VKBase $vkObject) { | 
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| 33 | |||
| 34 | /**  | 
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| 35 | * Returns detailed information on users  | 
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| 36 | * @param string[] $usersIDs  | 
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| 37 | * @param array $requestFields  | 
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| 38 | * @param string $nameCase  | 
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| 39 | * @return mixed  | 
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| 40 | * @throws VKException  | 
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| 41 | */  | 
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| 42 |     public function get($usersIDs, $requestFields = self::standardFields, $nameCase = 'nom') { | 
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| 58 | |||
| 59 | /**  | 
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| 60 | * Returns a list of users matching the search criteria  | 
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| 61 | * @param string $searchQuery  | 
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| 62 | * @param int $isOnline  | 
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| 63 | * @param array $requestFields  | 
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| 64 | * @param int $sortBy  | 
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| 65 | * @param int $displayCount  | 
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| 66 | * @return array  | 
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| 67 | * @throws VKException  | 
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| 68 | */  | 
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| 69 |     public function search($searchQuery, $isOnline = 1, $requestFields = self::standardFields, $sortBy = 0, $displayCount = 5) { | 
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| 88 | |||
| 89 | /**  | 
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| 90 | * Returns information whether a user installed the application  | 
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| 91 | * @param int $userID  | 
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| 92 | * @return mixed  | 
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| 93 | * @throws VKException  | 
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| 94 | */  | 
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| 95 |     public function isAppUser($userID) { | 
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| 102 | |||
| 103 | /**  | 
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| 104 | * Returns a list of IDs of users and communities followed by the user  | 
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| 105 | * @param int $userID  | 
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| 106 | * @param int $combineResults  | 
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| 107 | * @param array $requestFields  | 
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| 108 | * @param int $resultCount  | 
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| 109 | * @return mixed  | 
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| 110 | * @throws VKException  | 
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| 111 | */  | 
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| 112 | View Code Duplication |     public function getSubscriptions($userID, $combineResults = 0, $requestFields = self::standardFields, $resultCount = 20) { | 
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| 122 | |||
| 123 | /**  | 
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| 124 | * Returns a list of IDs of followers of the user in question, sorted by date added, most recent first  | 
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| 125 | * @param int $userID  | 
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| 126 | * @param int $setOffset  | 
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| 127 | * @param int $displayCount  | 
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| 128 | * @param array $requestFields  | 
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| 129 | * @param string $nameCase  | 
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| 130 | * @return mixed  | 
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| 131 | * @throws VKException  | 
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| 132 | */  | 
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| 133 | View Code Duplication |     public function getFollowers($userID, $setOffset = 0, $displayCount = 100, $requestFields = self::standardFields, $nameCase = 'nom') { | 
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| 144 | |||
| 145 | /**  | 
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| 146 | * Get Nearby Users Based On Current Latitude and Longitude  | 
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| 147 | * @param float $currentLatitude  | 
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| 148 | * @param float $currentLongitude  | 
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| 149 | * @param int $setTimeOut  | 
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| 150 | * @param int $setRadius  | 
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| 151 | * @param array $requestFields  | 
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| 152 | * @param string $nameCase  | 
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| 153 | * @return mixed  | 
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| 154 | * @throws VKException  | 
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| 155 | */  | 
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| 156 |     public function getNearby($currentLatitude, $currentLongitude, $setTimeOut = 7200, $setRadius = 1, $requestFields = self::standardFields, $nameCase = 'nom') { | 
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| 168 | |||
| 169 | /**  | 
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| 170 | * Return fields which are allowed to be used  | 
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| 171 | * @param $fieldsArray  | 
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| 172 | * @return string  | 
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| 173 | */  | 
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| 174 |     private function returnAllowedFields($fieldsArray) { | 
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| 184 | |||
| 185 | /**  | 
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| 186 | * Return Allowed Name Case  | 
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| 187 | * @param string $ncValue  | 
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| 188 | * @return string  | 
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| 189 | */  | 
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| 190 |     private function returnAllowedNC($ncValue) { | 
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| 197 | }  | 
            
This check looks for a call to a parent method whose name is different than the method from which it is called.
Consider the following code:
The
getFirstName()method in theSoncalls the wrong method in the parent class.