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 | ||
| 8 | class Vote extends ActiveRecordModelExtender | ||
| 9 | { | ||
| 10 | |||
| 11 | /** | ||
| 12 | * @var string $tableName name of the database table. | ||
| 13 | */ | ||
| 14 | protected $tableName = "ramverk1_votes"; | ||
| 15 | |||
| 16 | /** | ||
| 17 | * Columns in the table. | ||
| 18 | * | ||
| 19 | * @var integer $id primary key auto incremented. | ||
| 20 | */ | ||
| 21 | public $id; | ||
| 22 | public $user; # question/answer/comment | ||
| 23 | public $parentId; # All posts have different ids | ||
| 24 | public $parentType; # post or comment | ||
| 25 | public $upVote; | ||
| 26 | public $downVote; | ||
| 27 | |||
| 28 | |||
| 29 | /** | ||
| 30 | * Return a vote | ||
| 31 | * @param string $sql | ||
| 32 | * @param array $params | ||
| 33 | * | ||
| 34 | * @return object | ||
| 35 | */ | ||
| 36 | 1 | public function getVote($sql, $params) | |
| 50 | |||
| 51 | /** | ||
| 52 | * Control if user has already liked or not | ||
| 53 | * @param string $user | ||
| 54 | * @param array $params | ||
| 55 | * | ||
| 56 | * @return bool | ||
| 57 | */ | ||
| 58 | 1 | View Code Duplication | public function like($user, $parentId, $parentType) | 
| 77 | |||
| 78 | /** | ||
| 79 | * Control if user has already liked or not | ||
| 80 | * @param string $user | ||
| 81 | * @param array $params | ||
| 82 | * | ||
| 83 | * @return bool | ||
| 84 | */ | ||
| 85 | 1 | View Code Duplication | public function dislike($user, $parentId, $parentType) | 
| 104 | } | ||
| 105 | 
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: