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 | ||
| 10 | class Backup_Status { | ||
| 11 | |||
| 12 | /** | ||
| 13 | * The filename for the backup file we are the tracking status of | ||
| 14 | * | ||
| 15 | * @var string | ||
| 16 | */ | ||
| 17 | private $filename = ''; | ||
| 18 | |||
| 19 | /** | ||
| 20 | * [$lock_handler description] | ||
| 21 | * | ||
| 22 | * @var LockHandler | ||
| 23 | */ | ||
| 24 | private $lock_handler = ''; | ||
| 25 | |||
| 26 | private $callback; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * @param string $id The unique id for the backup job | ||
| 30 | */ | ||
| 31 | 	public function __construct( $id ) { | ||
| 35 | |||
| 36 | /** | ||
| 37 | * Start the tracking a backup process. | ||
| 38 | * | ||
| 39 | * This creates a backup running file and issues a file lock. This prevents duplicate | ||
| 40 | * instances of this backup process running concurrently and allows us to detect if | ||
| 41 | * the PHP thread running the process is killed as that will clear the lock. | ||
| 42 | * | ||
| 43 | * @param string $backup_filename The filename for the backup file that we're tracking | ||
| 44 | * @param string $status_message The initial status for the backup process | ||
| 45 | * | ||
| 46 | * @return boolean Whether the backup process was success marked as started | ||
| 47 | */ | ||
| 48 | 	public function start( $backup_filename, $status_message ) { | ||
| 64 | |||
| 65 | /** | ||
| 66 | * Mark a backup process as finished. | ||
| 67 | * | ||
| 68 | * This removes the file lock and deletes the running file. | ||
| 69 | */ | ||
| 70 | 	public function finish() { | ||
| 83 | |||
| 84 | /** | ||
| 85 | * Check if the backup has been started by checking if the running file | ||
| 86 | * exists. | ||
| 87 | * | ||
| 88 | * @return boolean Whether the backup process has been started | ||
| 89 | */ | ||
| 90 | 	public function is_started() { | ||
| 93 | |||
| 94 | 	public function is_running() { | ||
| 109 | |||
| 110 | /** | ||
| 111 | * If the running file exists but isn't locked then the thread that | ||
| 112 | * the backup process is running in must have been killed. | ||
| 113 | * | ||
| 114 | * You should only be running this command from a separate thread | ||
| 115 | * | ||
| 116 | * @return boolean Whether the backup process has crashed or not | ||
| 117 | */ | ||
| 118 | 	public function has_crashed() { | ||
| 121 | |||
| 122 | /** | ||
| 123 | * Handle a process that's previouly crashed. | ||
| 124 | * | ||
| 125 | * Delete the partially created backup if it exists and then run the standard | ||
| 126 | * cleanup tasks and set an error message for the user. | ||
| 127 | * | ||
| 128 | * @return bool Whether the crash was handled or not | ||
| 129 | */ | ||
| 130 | 	public function cleanup_after_crash() { | ||
| 151 | |||
| 152 | /** | ||
| 153 | * Catch fatal errors and react accordingly. | ||
| 154 | * | ||
| 155 | * Hooked into the shutdown action. If we've shutdown because of a Fatal error | ||
| 156 | * then we cleanup and set an error message for the user. | ||
| 157 | */ | ||
| 158 | 	public function catch_fatals() { | ||
| 180 | |||
| 181 | /** | ||
| 182 | * Get the filepath for the backup file we're tracking | ||
| 183 | * | ||
| 184 | * @return string The path to the backup file | ||
| 185 | */ | ||
| 186 | 	public function get_backup_filename() { | ||
| 198 | |||
| 199 | /** | ||
| 200 | * Get the status of the running backup. | ||
| 201 | * | ||
| 202 | * @return string | ||
| 203 | */ | ||
| 204 | 	public function get_status() { | ||
| 219 | |||
| 220 | /** | ||
| 221 | * Set the status of the running backup | ||
| 222 | * | ||
| 223 | * @param string $message | ||
| 224 | * | ||
| 225 | * @return null | ||
| 226 | */ | ||
| 227 | 	public function set_status( $message ) { | ||
| 247 | |||
| 248 | /** | ||
| 249 | * Get the time that the current running backup was started | ||
| 250 | * | ||
| 251 | * @return int $timestamp | ||
| 252 | */ | ||
| 253 | 	public function get_start_time() { | ||
| 268 | |||
| 269 | /** | ||
| 270 | * Get the path to the backup running file that stores the running backup status | ||
| 271 | * | ||
| 272 | * @return string | ||
| 273 | */ | ||
| 274 | 	public function get_status_filepath() { | ||
| 277 | |||
| 278 | 	public function set_status_callback( $callback ) { | ||
| 281 | } | ||
| 282 | 
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: