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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| 9 | class SyncerCommand  | 
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| 10 | { | 
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| 11 | |||
| 12 | /**  | 
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| 13 | * Will be returned when program exits.  | 
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| 14 | * @var integer  | 
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| 15 | */  | 
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| 16 | protected $exitCode = 0;  | 
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| 17 | |||
| 18 | /**  | 
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| 19 | * The mode the program is running in.  | 
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| 20 | * @var string  | 
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| 21 | */  | 
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| 22 | protected $mode;  | 
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| 23 | |||
| 24 | /**  | 
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| 25 | * Instance of the FileCollector class.  | 
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| 26 | * @var FileCollector  | 
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| 27 | */  | 
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| 28 | protected $fileCollector;  | 
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| 29 | |||
| 30 | /**  | 
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| 31 | * Instance of the EnvironmentFilder class.  | 
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| 32 | * @var EnvironmentFinder  | 
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| 33 | */  | 
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| 34 | protected $envFinder;  | 
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| 35 | |||
| 36 | /**  | 
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| 37 | * Instance of the TableBuilder class.  | 
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| 38 | * @var TableBuilder  | 
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| 39 | */  | 
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| 40 | protected $tableBuilder;  | 
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| 41 | |||
| 42 | /**  | 
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| 43 | * The source colde folder that will be inspected.  | 
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| 44 | * @var string  | 
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| 45 | */  | 
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| 46 | protected $folder;  | 
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| 47 | |||
| 48 | /**  | 
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| 49 | * Creates a new instance of the SyncerCommand.  | 
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| 50 | * @param FileCollector $fileCollector File Collector.  | 
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| 51 | * @param EnvironmentFinder $envFinder Environment Variable Filder.  | 
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| 52 | * @param TableBuilder $tableBuilder Table Builder.  | 
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| 53 | */  | 
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| 54 | public function __construct(FileCollector $fileCollector, EnvironmentFinder $envFinder, TableBuilder $tableBuilder)  | 
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| 60 | |||
| 61 | /**  | 
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| 62 | * Runs the command.  | 
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| 63 | * @param array $arguments Command line arguments.  | 
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| 64 | * @return void  | 
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| 65 | */  | 
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| 66 | public function handle(array $arguments)  | 
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| 92 | |||
| 93 | /**  | 
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| 94 | * Gets a list of the environment variables defined in the  | 
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| 95 | * source code, .env and .env.example file.  | 
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| 96 | * @return array  | 
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| 97 | */  | 
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| 98 | protected function getEnvironmentVariables()  | 
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| 112 | |||
| 113 | /**  | 
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| 114 | * Takes the list of environment variables defined and creates  | 
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| 115 | * a results array showing each variable and where it is or is not  | 
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| 116 | * defined.  | 
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| 117 | * @param array $envData Environment Variable Data.  | 
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| 118 | * @return array  | 
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| 119 | */  | 
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| 120 | protected function getResults(array $envData)  | 
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| 135 | |||
| 136 | /**  | 
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| 137 | * Looks through all the current env variables from all  | 
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| 138 | * sources and makes a master list of all of them.  | 
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| 139 | * @param array $currentEnvs Current Env Variables.  | 
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| 140 | * @return array  | 
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| 141 | */  | 
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| 142 | protected function mergeEnvs(array $currentEnvs)  | 
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| 150 | |||
| 151 | /**  | 
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| 152 | * If a variable is defined in the source code but  | 
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| 153 | * not defined in the .env.example file we write  | 
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| 154 | * to the message and set response to 1  | 
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| 155 | * @param array $results Environment Variable Results.  | 
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| 156 | * @return void  | 
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| 157 | */  | 
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| 158 | View Code Duplication | protected function checkForCiBuild(array $results)  | 
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| 166 | |||
| 167 | /**  | 
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| 168 | * If a variable is defined in the source code but  | 
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| 169 | * not defined in the .env file we write  | 
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| 170 | * to the message and set response to 1  | 
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| 171 | * @param array $results Environment Variable Results.  | 
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| 172 | * @return void  | 
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| 173 | */  | 
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| 174 | View Code Duplication | protected function checkForDeploy(array $results)  | 
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| 182 | |||
| 183 | /**  | 
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| 184 | * Collects the command line arguments.  | 
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| 185 | * @param array $arguments Command line arguments.  | 
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| 186 | * @return boolean  | 
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| 187 | */  | 
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| 188 | protected function argumentsValid(array $arguments)  | 
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| 214 | }  | 
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| 215 | 
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: