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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| 20 | class UserApi extends AbstractApi  | 
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| 21 | { | 
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| 22 | /**  | 
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| 23 | * @var UserFactory  | 
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| 24 | */  | 
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| 25 | private $userFactory;  | 
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| 26 | |||
| 27 | /**  | 
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| 28 | * @var Serializer  | 
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| 29 | */  | 
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| 30 | private $serializer;  | 
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| 31 | |||
| 32 | public function __construct(ClientInterface $httpClient, LoggerInterface $logger, UserFactory $userFactory, Serializer $serializer)  | 
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| 38 | |||
| 39 | public function isAuthDataValid(string $login, string $password): bool  | 
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| 55 | |||
| 56 | public function authenticate(string $login, string $password): Auth  | 
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| 78 | |||
| 79 | public function logout(Auth $auth): bool  | 
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| 97 | |||
| 98 | /**  | 
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| 99 | * Get user subscribers by user login  | 
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| 100 | *  | 
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| 101 | * @param string $login  | 
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| 102 | *  | 
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| 103 | * @return User[]  | 
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| 104 | *  | 
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| 105 | * @throws ApiException  | 
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| 106 | * @throws InvalidResponseException  | 
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| 107 | * @throws UserNotFoundException  | 
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| 108 | */  | 
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| 109 | View Code Duplication | public function getUserSubscribersByLogin(string $login): array  | 
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| 125 | |||
| 126 | /**  | 
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| 127 | * Get user subscribers by user id  | 
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| 128 | *  | 
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| 129 | * @param int $id  | 
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| 130 | *  | 
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| 131 | * @return User[]  | 
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| 132 | *  | 
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| 133 | * @throws ApiException  | 
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| 134 | * @throws InvalidResponseException  | 
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| 135 | * @throws UserNotFoundException  | 
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| 136 | */  | 
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| 137 | View Code Duplication | public function getUserSubscribersById(int $id): array  | 
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| 153 | |||
| 154 | /**  | 
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| 155 | * Get user subscriptions by user login  | 
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| 156 | *  | 
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| 157 | * @param string $login  | 
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| 158 | *  | 
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| 159 | * @return User[]  | 
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| 160 | *  | 
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| 161 | * @throws ApiException  | 
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| 162 | * @throws InvalidResponseException  | 
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| 163 | * @throws UserNotFoundException  | 
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| 164 | */  | 
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| 165 | View Code Duplication | public function getUserSubscriptionsByLogin(string $login): array  | 
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| 181 | |||
| 182 | /**  | 
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| 183 | * Get user subscriptions by user id  | 
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| 184 | *  | 
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| 185 | * @param int $id  | 
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| 186 | *  | 
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| 187 | * @return User[]  | 
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| 188 | *  | 
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| 189 | * @throws ApiException  | 
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| 190 | * @throws InvalidResponseException  | 
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| 191 | * @throws UserNotFoundException  | 
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| 192 | */  | 
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| 193 | View Code Duplication | public function getUserSubscriptionsById(int $id): array  | 
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| 209 | |||
| 210 | /**  | 
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| 211 | * Get single user by login  | 
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| 212 | *  | 
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| 213 | * @param string $login  | 
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| 214 | *  | 
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| 215 | * @return User  | 
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| 216 | *  | 
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| 217 | * @throws UserNotFoundException  | 
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| 218 | * @throws RequestException  | 
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| 219 | */  | 
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| 220 | View Code Duplication | public function getUserByLogin(string $login): User  | 
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| 236 | |||
| 237 | /**  | 
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| 238 | * Get single user by id  | 
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| 239 | *  | 
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| 240 | * @param int $id  | 
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| 241 | *  | 
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| 242 | * @return User  | 
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| 243 | *  | 
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| 244 | * @throws UserNotFoundException  | 
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| 245 | * @throws RequestException  | 
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| 246 | */  | 
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| 247 | View Code Duplication | public function getUserById(int $id): User  | 
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| 263 | |||
| 264 | /**  | 
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| 265 | * Finds and updates or create new user from API response data  | 
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| 266 | *  | 
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| 267 | * @param array $userInfo  | 
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| 268 | *  | 
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| 269 | * @return User  | 
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| 270 | *  | 
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| 271 | * @throws ApiException  | 
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| 272 | * @throws InvalidResponseException  | 
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| 273 | */  | 
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| 274 | private function getUserFromUserInfo(array $userInfo): User  | 
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| 280 | |||
| 281 | /**  | 
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| 282 | * Get array of User objects from API response containing user list  | 
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| 283 | *  | 
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| 284 | * @param array $users  | 
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| 285 | *  | 
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| 286 | * @return User[]  | 
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| 287 | *  | 
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| 288 | * @throws ApiException  | 
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| 289 | * @throws InvalidResponseException  | 
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| 290 | */  | 
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| 291 | private function getUsersFromList(array $users = []): array  | 
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| 304 | }  | 
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| 305 | 
This check looks from parameters that have been defined for a function or method, but which are not used in the method body.