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 | ||
| 15 | class Constants extends Module { | ||
| 16 | /** | ||
| 17 | * Name of the constants checksum option. | ||
| 18 | * | ||
| 19 | * @var string | ||
| 20 | */ | ||
| 21 | const CONSTANTS_CHECKSUM_OPTION_NAME = 'jetpack_constants_sync_checksum'; | ||
| 22 | |||
| 23 | /** | ||
| 24 | * Name of the transient for locking constants. | ||
| 25 | * | ||
| 26 | * @var string | ||
| 27 | */ | ||
| 28 | const CONSTANTS_AWAIT_TRANSIENT_NAME = 'jetpack_sync_constants_await'; | ||
| 29 | |||
| 30 | /** | ||
| 31 | * Sync module name. | ||
| 32 | * | ||
| 33 | * @access public | ||
| 34 | * | ||
| 35 | * @return string | ||
| 36 | */ | ||
| 37 | 	public function name() { | ||
| 40 | |||
| 41 | /** | ||
| 42 | * Initialize constants action listeners. | ||
| 43 | * | ||
| 44 | * @access public | ||
| 45 | * | ||
| 46 | * @param callable $callable Action handler callable. | ||
| 47 | */ | ||
| 48 | 	public function init_listeners( $callable ) { | ||
| 51 | |||
| 52 | /** | ||
| 53 | * Initialize constants action listeners for full sync. | ||
| 54 | * | ||
| 55 | * @access public | ||
| 56 | * | ||
| 57 | * @param callable $callable Action handler callable. | ||
| 58 | */ | ||
| 59 | 	public function init_full_sync_listeners( $callable ) { | ||
| 62 | |||
| 63 | /** | ||
| 64 | * Initialize the module in the sender. | ||
| 65 | * | ||
| 66 | * @access public | ||
| 67 | */ | ||
| 68 | 	public function init_before_send() { | ||
| 74 | |||
| 75 | /** | ||
| 76 | * Perform module cleanup. | ||
| 77 | * Deletes any transients and options that this module uses. | ||
| 78 | * Usually triggered when uninstalling the plugin. | ||
| 79 | * | ||
| 80 | * @access public | ||
| 81 | */ | ||
| 82 | 	public function reset_data() { | ||
| 86 | |||
| 87 | /** | ||
| 88 | * Set the constants whitelist. | ||
| 89 | * | ||
| 90 | * @access public | ||
| 91 | * @todo We don't seem to use this one. Should we remove it? | ||
| 92 | * | ||
| 93 | * @param array $constants The new constants whitelist. | ||
| 94 | */ | ||
| 95 | 	public function set_constants_whitelist( $constants ) { | ||
| 98 | |||
| 99 | /** | ||
| 100 | * Get the constants whitelist. | ||
| 101 | * | ||
| 102 | * @access public | ||
| 103 | * | ||
| 104 | * @return array The constants whitelist. | ||
| 105 | */ | ||
| 106 | 	public function get_constants_whitelist() { | ||
| 109 | |||
| 110 | /** | ||
| 111 | * Enqueue the constants actions for full sync. | ||
| 112 | * | ||
| 113 | * @access public | ||
| 114 | * | ||
| 115 | * @param array $config Full sync configuration for this sync module. | ||
| 116 | * @param int $max_items_to_enqueue Maximum number of items to enqueue. | ||
| 117 | * @param boolean $state True if full sync has finished enqueueing this module, false otherwise. | ||
| 118 | * | ||
| 119 | * @return array Number of actions enqueued, and next module state. | ||
| 120 | */ | ||
| 121 | 	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable | ||
| 134 | |||
| 135 | /** | ||
| 136 | * Send the constants actions for full sync. | ||
| 137 | * | ||
| 138 | * @access public | ||
| 139 | * | ||
| 140 | * @param array $config Full sync configuration for this sync module. | ||
| 141 | * @param int $send_until The timestamp until the current request can send. | ||
| 142 | * @param array $state This module Full Sync status. | ||
| 143 | * | ||
| 144 | * @return array This module Full Sync status. | ||
| 145 | */ | ||
| 146 | 	public function send_full_sync_actions( $config, $send_until, $state ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable | ||
| 153 | |||
| 154 | /** | ||
| 155 | * Retrieve an estimated number of actions that will be enqueued. | ||
| 156 | * | ||
| 157 | * @access public | ||
| 158 | * | ||
| 159 | * @param array $config Full sync configuration for this sync module. | ||
| 160 | * | ||
| 161 | * @return array Number of items yet to be enqueued. | ||
| 162 | */ | ||
| 163 | 	public function estimate_full_sync_actions( $config ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable | ||
| 166 | |||
| 167 | /** | ||
| 168 | * Retrieve the actions that will be sent for this module during a full sync. | ||
| 169 | * | ||
| 170 | * @access public | ||
| 171 | * | ||
| 172 | * @return array Full sync actions of this module. | ||
| 173 | */ | ||
| 174 | 	public function get_full_sync_actions() { | ||
| 177 | |||
| 178 | /** | ||
| 179 | * Sync the constants if we're supposed to. | ||
| 180 | * | ||
| 181 | * @access public | ||
| 182 | */ | ||
| 183 | 	public function maybe_sync_constants() { | ||
| 217 | |||
| 218 | /** | ||
| 219 | * Retrieve all constants as per the current constants whitelist. | ||
| 220 | * Public so that we don't have to store an option for each constant. | ||
| 221 | * | ||
| 222 | * @access public | ||
| 223 | * | ||
| 224 | * @return array All constants. | ||
| 225 | */ | ||
| 226 | 	public function get_all_constants() { | ||
| 234 | |||
| 235 | /** | ||
| 236 | * Retrieve the value of a constant. | ||
| 237 | * Used as a wrapper to standartize access to constants. | ||
| 238 | * | ||
| 239 | * @access private | ||
| 240 | * | ||
| 241 | * @param string $constant Constant name. | ||
| 242 | * | ||
| 243 | * @return mixed Return value of the constant. | ||
| 244 | */ | ||
| 245 | 	private function get_constant( $constant ) { | ||
| 250 | |||
| 251 | /** | ||
| 252 | * Expand the constants within a hook before they are serialized and sent to the server. | ||
| 253 | * | ||
| 254 | * @access public | ||
| 255 | * | ||
| 256 | * @param array $args The hook parameters. | ||
| 257 | * | ||
| 258 | * @return array $args The hook parameters. | ||
| 259 | */ | ||
| 260 | 	public function expand_constants( $args ) { | ||
| 274 | |||
| 275 | /** | ||
| 276 | * Return Total number of objects. | ||
| 277 | * | ||
| 278 | * @param array $config Full Sync config. | ||
| 279 | * | ||
| 280 | * @return int total | ||
| 281 | */ | ||
| 282 | 	public function total( $config ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable | ||
| 285 | |||
| 286 | /** | ||
| 287 | * Retrieve a set of constants by their IDs. | ||
| 288 | * | ||
| 289 | * @access public | ||
| 290 | * | ||
| 291 | * @param string $object_type Object type. | ||
| 292 | * @param array $ids Object IDs. | ||
| 293 | * @return array Array of objects. | ||
| 294 | */ | ||
| 295 | View Code Duplication | 	public function get_objects_by_id( $object_type, $ids ) { | |
| 296 | 		if ( empty( $ids ) || empty( $object_type ) || 'constant' !== $object_type ) { | ||
| 297 | return array(); | ||
| 298 | } | ||
| 299 | |||
| 300 | $objects = array(); | ||
| 301 | 		foreach ( (array) $ids as $id ) { | ||
| 302 | $object = $this->get_object_by_id( $object_type, $id ); | ||
| 303 | |||
| 304 | 			if ( 'all' === $id ) { | ||
| 305 | // If all was requested it contains all options and can simply be returned. | ||
| 306 | return $object; | ||
| 307 | } | ||
| 308 | $objects[ $id ] = $object; | ||
| 309 | } | ||
| 310 | |||
| 311 | return $objects; | ||
| 312 | } | ||
| 313 | |||
| 314 | /** | ||
| 315 | * Retrieve a constant by its name. | ||
| 316 | * | ||
| 317 | * @access public | ||
| 318 | * | ||
| 319 | * @param string $object_type Type of the sync object. | ||
| 320 | * @param string $id ID of the sync object. | ||
| 321 | * @return mixed Value of Constant. | ||
| 322 | */ | ||
| 323 | 	public function get_object_by_id( $object_type, $id ) { | ||
| 336 | |||
| 337 | } | ||
| 338 | 
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: