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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| 16 | class Terms extends Module { | 
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| 17 | /**  | 
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| 18 | * Whitelist for taxonomies we want to sync.  | 
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| 19 | *  | 
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| 20 | * @access private  | 
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| 21 | *  | 
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| 22 | * @var array  | 
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| 23 | */  | 
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| 24 | private $taxonomy_whitelist;  | 
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| 25 | |||
| 26 | /**  | 
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| 27 | * Sync module name.  | 
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| 28 | *  | 
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| 29 | * @access public  | 
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| 30 | *  | 
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| 31 | * @return string  | 
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| 32 | */  | 
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| 33 | 	public function name() { | 
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| 36 | |||
| 37 | /**  | 
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| 38 | * Allows WordPress.com servers to retrieve term-related objects via the sync API.  | 
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| 39 | *  | 
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| 40 | * @param string $object_type The type of object.  | 
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| 41 | * @param int $id The id of the object.  | 
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| 42 | *  | 
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| 43 | * @return bool|object A WP_Term object, or a row from term_taxonomy table depending on object type.  | 
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| 44 | */  | 
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| 45 | 	public function get_object_by_id( $object_type, $id ) { | 
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| 77 | |||
| 78 | /**  | 
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| 79 | * Initialize terms action listeners.  | 
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| 80 | *  | 
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| 81 | * @access public  | 
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| 82 | *  | 
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| 83 | * @param callable $callable Action handler callable.  | 
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| 84 | */  | 
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| 85 | 	public function init_listeners( $callable ) { | 
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| 96 | |||
| 97 | /**  | 
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| 98 | * Initialize terms action listeners for full sync.  | 
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| 99 | *  | 
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| 100 | * @access public  | 
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| 101 | *  | 
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| 102 | * @param callable $callable Action handler callable.  | 
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| 103 | */  | 
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| 104 | 	public function init_full_sync_listeners( $callable ) { | 
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| 107 | |||
| 108 | /**  | 
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| 109 | * Initialize the module in the sender.  | 
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| 110 | *  | 
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| 111 | * @access public  | 
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| 112 | */  | 
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| 113 | 	public function init_before_send() { | 
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| 117 | |||
| 118 | /**  | 
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| 119 | * Enqueue the terms actions for full sync.  | 
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| 120 | *  | 
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| 121 | * @access public  | 
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| 122 | *  | 
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| 123 | * @param array $config Full sync configuration for this sync module.  | 
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| 124 | * @param int $max_items_to_enqueue Maximum number of items to enqueue.  | 
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| 125 | * @param boolean $state True if full sync has finished enqueueing this module, false otherwise.  | 
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| 126 | * @return array Number of actions enqueued, and next module state.  | 
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| 127 | */  | 
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| 128 | 	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) { | 
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| 132 | |||
| 133 | /**  | 
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| 134 | * Retrieve the WHERE SQL clause based on the module config.  | 
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| 135 | *  | 
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| 136 | * @access private  | 
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| 137 | *  | 
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| 138 | * @param array $config Full sync configuration for this sync module.  | 
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| 139 | * @return string WHERE SQL clause, or `null` if no comments are specified in the module config.  | 
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| 140 | */  | 
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| 141 | View Code Duplication | 	private function get_where_sql( $config ) { | 
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| 150 | |||
| 151 | /**  | 
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| 152 | * Retrieve an estimated number of actions that will be enqueued.  | 
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| 153 | *  | 
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| 154 | * @access public  | 
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| 155 | *  | 
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| 156 | * @param array $config Full sync configuration for this sync module.  | 
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| 157 | * @return int Number of items yet to be enqueued.  | 
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| 158 | */  | 
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| 159 | View Code Duplication | 	public function estimate_full_sync_actions( $config ) { | 
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| 174 | |||
| 175 | /**  | 
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| 176 | * Retrieve the actions that will be sent for this module during a full sync.  | 
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| 177 | *  | 
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| 178 | * @access public  | 
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| 179 | *  | 
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| 180 | * @return array Full sync actions of this module.  | 
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| 181 | */  | 
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| 182 | 	public function get_full_sync_actions() { | 
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| 185 | |||
| 186 | /**  | 
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| 187 | * Handler for creating and updating terms.  | 
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| 188 | *  | 
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| 189 | * @access public  | 
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| 190 | *  | 
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| 191 | * @param int $term_id Term ID.  | 
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| 192 | * @param int $tt_id Term taxonomy ID.  | 
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| 193 | * @param string $taxonomy Taxonomy slug.  | 
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| 194 | */  | 
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| 195 | 	public function save_term_handler( $term_id, $tt_id, $taxonomy ) { | 
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| 225 | |||
| 226 | /**  | 
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| 227 | * Filter blacklisted taxonomies.  | 
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| 228 | *  | 
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| 229 | * @access public  | 
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| 230 | *  | 
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| 231 | * @param array $args Hook args.  | 
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| 232 | * @return array|boolean False if not whitelisted, the original hook args otherwise.  | 
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| 233 | */  | 
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| 234 | 	public function filter_blacklisted_taxonomies( $args ) { | 
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| 243 | |||
| 244 | /**  | 
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| 245 | * Set the taxonomy whitelist.  | 
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| 246 | *  | 
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| 247 | * @access public  | 
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| 248 | *  | 
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| 249 | * @param array $taxonomies The new taxonomyy whitelist.  | 
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| 250 | */  | 
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| 251 | 	public function set_taxonomy_whitelist( $taxonomies ) { | 
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| 254 | |||
| 255 | /**  | 
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| 256 | * Set module defaults.  | 
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| 257 | * Define the taxonomy whitelist to be the default one.  | 
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| 258 | *  | 
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| 259 | * @access public  | 
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| 260 | */  | 
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| 261 | 	public function set_defaults() { | 
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| 264 | |||
| 265 | /**  | 
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| 266 | * Expand the term taxonomy IDs to terms within a hook before they are serialized and sent to the server.  | 
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| 267 | *  | 
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| 268 | * @access public  | 
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| 269 | *  | 
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| 270 | * @param array $args The hook parameters.  | 
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| 271 | * @return array $args The expanded hook parameters.  | 
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| 272 | */  | 
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| 273 | 	public function expand_term_taxonomy_id( $args ) { | 
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| 288 | |||
| 289 | /**  | 
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| 290 | * Gets a term object based on a given row from the term_relationships database table.  | 
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| 291 | *  | 
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| 292 | * @access public  | 
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| 293 | *  | 
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| 294 | * @param object $relationship A row object from the term_relationships table.  | 
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| 295 | * @return object|bool A term object, or false if term taxonomy doesn't exist.  | 
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| 296 | */  | 
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| 297 | 	public function expand_terms_for_relationship( $relationship ) { | 
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| 300 | }  | 
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| 301 | 
This check looks for access to properties that are not accessible from the current context.
If you need to make a property accessible to another context you can either raise its visibility level or provide an accessible getter in the defining class.