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   1  <?php
   2  /**
   3   * Plugin API: WP_Hook class
   4   *
   5   * @package WordPress
   6   * @subpackage Plugin
   7   * @since 4.7.0
   8   */
   9  
  10  /**
  11   * Core class used to implement action and filter hook functionality.
  12   *
  13   * @since 4.7.0
  14   *
  15   * @see Iterator
  16   * @see ArrayAccess
  17   */
  18  #[AllowDynamicProperties]
  19  final class WP_Hook implements Iterator, ArrayAccess {
  20  
  21      /**
  22       * Hook callbacks.
  23       *
  24       * @since 4.7.0
  25       * @var array
  26       */
  27      public $callbacks = array();
  28  
  29      /**
  30       * Priorities list.
  31       *
  32       * @since 6.4.0
  33       * @var array
  34       */
  35      protected $priorities = array();
  36  
  37      /**
  38       * The priority keys of actively running iterations of a hook.
  39       *
  40       * @since 4.7.0
  41       * @var array
  42       */
  43      private $iterations = array();
  44  
  45      /**
  46       * The current priority of actively running iterations of a hook.
  47       *
  48       * @since 4.7.0
  49       * @var array
  50       */
  51      private $current_priority = array();
  52  
  53      /**
  54       * Number of levels this hook can be recursively called.
  55       *
  56       * @since 4.7.0
  57       * @var int
  58       */
  59      private $nesting_level = 0;
  60  
  61      /**
  62       * Flag for if we're currently doing an action, rather than a filter.
  63       *
  64       * @since 4.7.0
  65       * @var bool
  66       */
  67      private $doing_action = false;
  68  
  69      /**
  70       * Adds a callback function to a filter hook.
  71       *
  72       * @since 4.7.0
  73       *
  74       * @param string   $hook_name     The name of the filter to add the callback to.
  75       * @param callable $callback      The callback to be run when the filter is applied.
  76       * @param int      $priority      The order in which the functions associated with a particular filter
  77       *                                are executed. Lower numbers correspond with earlier execution,
  78       *                                and functions with the same priority are executed in the order
  79       *                                in which they were added to the filter.
  80       * @param int      $accepted_args The number of arguments the function accepts.
  81       */
  82  	public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
  83          if ( null === $priority ) {
  84              $priority = 0;
  85          }
  86  
  87          $idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
  88  
  89          $priority_existed = isset( $this->callbacks[ $priority ] );
  90  
  91          $this->callbacks[ $priority ][ $idx ] = array(
  92              'function'      => $callback,
  93              'accepted_args' => (int) $accepted_args,
  94          );
  95  
  96          // If we're adding a new priority to the list, put them back in sorted order.
  97          if ( ! $priority_existed && count( $this->callbacks ) > 1 ) {
  98              ksort( $this->callbacks, SORT_NUMERIC );
  99          }
 100  
 101          $this->priorities = array_keys( $this->callbacks );
 102  
 103          if ( $this->nesting_level > 0 ) {
 104              $this->resort_active_iterations( $priority, $priority_existed );
 105          }
 106      }
 107  
 108      /**
 109       * Handles resetting callback priority keys mid-iteration.
 110       *
 111       * @since 4.7.0
 112       *
 113       * @param false|int $new_priority     Optional. The priority of the new filter being added. Default false,
 114       *                                    for no priority being added.
 115       * @param bool      $priority_existed Optional. Flag for whether the priority already existed before the new
 116       *                                    filter was added. Default false.
 117       */
 118  	private function resort_active_iterations( $new_priority = false, $priority_existed = false ) {
 119          $new_priorities = $this->priorities;
 120  
 121          // If there are no remaining hooks, clear out all running iterations.
 122          if ( ! $new_priorities ) {
 123              foreach ( $this->iterations as $index => $iteration ) {
 124                  $this->iterations[ $index ] = $new_priorities;
 125              }
 126  
 127              return;
 128          }
 129  
 130          $min = min( $new_priorities );
 131  
 132          foreach ( $this->iterations as $index => &$iteration ) {
 133              $current = current( $iteration );
 134  
 135              // If we're already at the end of this iteration, just leave the array pointer where it is.
 136              if ( false === $current ) {
 137                  continue;
 138              }
 139  
 140              $iteration = $new_priorities;
 141  
 142              if ( $current < $min ) {
 143                  array_unshift( $iteration, $current );
 144                  continue;
 145              }
 146  
 147              while ( current( $iteration ) < $current ) {
 148                  if ( false === next( $iteration ) ) {
 149                      break;
 150                  }
 151              }
 152  
 153              // If we have a new priority that didn't exist, but ::apply_filters() or ::do_action() thinks it's the current priority...
 154              if ( $new_priority === $this->current_priority[ $index ] && ! $priority_existed ) {
 155                  /*
 156                   * ...and the new priority is the same as what $this->iterations thinks is the previous
 157                   * priority, we need to move back to it.
 158                   */
 159  
 160                  if ( false === current( $iteration ) ) {
 161                      // If we've already moved off the end of the array, go back to the last element.
 162                      $prev = end( $iteration );
 163                  } else {
 164                      // Otherwise, just go back to the previous element.
 165                      $prev = prev( $iteration );
 166                  }
 167  
 168                  if ( false === $prev ) {
 169                      // Start of the array. Reset, and go about our day.
 170                      reset( $iteration );
 171                  } elseif ( $new_priority !== $prev ) {
 172                      // Previous wasn't the same. Move forward again.
 173                      next( $iteration );
 174                  }
 175              }
 176          }
 177  
 178          unset( $iteration );
 179      }
 180  
 181      /**
 182       * Removes a callback function from a filter hook.
 183       *
 184       * @since 4.7.0
 185       *
 186       * @param string                $hook_name The filter hook to which the function to be removed is hooked.
 187       * @param callable|string|array $callback  The callback to be removed from running when the filter is applied.
 188       *                                         This method can be called unconditionally to speculatively remove
 189       *                                         a callback that may or may not exist.
 190       * @param int                   $priority  The exact priority used when adding the original filter callback.
 191       * @return bool Whether the callback existed before it was removed.
 192       */
 193  	public function remove_filter( $hook_name, $callback, $priority ) {
 194          if ( null === $priority ) {
 195              $priority = 0;
 196          }
 197  
 198          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
 199  
 200          $exists = isset( $function_key, $this->callbacks[ $priority ][ $function_key ] );
 201  
 202          if ( $exists ) {
 203              unset( $this->callbacks[ $priority ][ $function_key ] );
 204  
 205              if ( ! $this->callbacks[ $priority ] ) {
 206                  unset( $this->callbacks[ $priority ] );
 207  
 208                  $this->priorities = array_keys( $this->callbacks );
 209  
 210                  if ( $this->nesting_level > 0 ) {
 211                      $this->resort_active_iterations();
 212                  }
 213              }
 214          }
 215  
 216          return $exists;
 217      }
 218  
 219      /**
 220       * Checks if a specific callback has been registered for this hook.
 221       *
 222       * When using the `$callback` argument, this function may return a non-boolean value
 223       * that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
 224       *
 225       * @since 4.7.0
 226       *
 227       * @param string                      $hook_name Optional. The name of the filter hook. Default empty.
 228       * @param callable|string|array|false $callback  Optional. The callback to check for.
 229       *                                               This method can be called unconditionally to speculatively check
 230       *                                               a callback that may or may not exist. Default false.
 231       * @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
 232       *                  anything registered. When checking a specific function, the priority
 233       *                  of that hook is returned, or false if the function is not attached.
 234       */
 235  	public function has_filter( $hook_name = '', $callback = false ) {
 236          if ( false === $callback ) {
 237              return $this->has_filters();
 238          }
 239  
 240          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );
 241  
 242          if ( ! $function_key ) {
 243              return false;
 244          }
 245  
 246          foreach ( $this->callbacks as $priority => $callbacks ) {
 247              if ( isset( $callbacks[ $function_key ] ) ) {
 248                  return $priority;
 249              }
 250          }
 251  
 252          return false;
 253      }
 254  
 255      /**
 256       * Checks if any callbacks have been registered for this hook.
 257       *
 258       * @since 4.7.0
 259       *
 260       * @return bool True if callbacks have been registered for the current hook, otherwise false.
 261       */
 262  	public function has_filters() {
 263          foreach ( $this->callbacks as $callbacks ) {
 264              if ( $callbacks ) {
 265                  return true;
 266              }
 267          }
 268  
 269          return false;
 270      }
 271  
 272      /**
 273       * Removes all callbacks from the current filter.
 274       *
 275       * @since 4.7.0
 276       *
 277       * @param int|false $priority Optional. The priority number to remove. Default false.
 278       */
 279  	public function remove_all_filters( $priority = false ) {
 280          if ( ! $this->callbacks ) {
 281              return;
 282          }
 283  
 284          if ( false === $priority ) {
 285              $this->callbacks  = array();
 286              $this->priorities = array();
 287          } elseif ( isset( $this->callbacks[ $priority ] ) ) {
 288              unset( $this->callbacks[ $priority ] );
 289              $this->priorities = array_keys( $this->callbacks );
 290          }
 291  
 292          if ( $this->nesting_level > 0 ) {
 293              $this->resort_active_iterations();
 294          }
 295      }
 296  
 297      /**
 298       * Calls the callback functions that have been added to a filter hook.
 299       *
 300       * @since 4.7.0
 301       *
 302       * @param mixed $value The value to filter.
 303       * @param array $args  Additional parameters to pass to the callback functions.
 304       *                     This array is expected to include $value at index 0.
 305       * @return mixed The filtered value after all hooked functions are applied to it.
 306       */
 307  	public function apply_filters( $value, $args ) {
 308          if ( ! $this->callbacks ) {
 309              return $value;
 310          }
 311  
 312          $nesting_level = $this->nesting_level++;
 313  
 314          $this->iterations[ $nesting_level ] = $this->priorities;
 315  
 316          $num_args = count( $args );
 317  
 318          do {
 319              $this->current_priority[ $nesting_level ] = current( $this->iterations[ $nesting_level ] );
 320  
 321              $priority = $this->current_priority[ $nesting_level ];
 322  
 323              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 324                  if ( ! $this->doing_action ) {
 325                      $args[0] = $value;
 326                  }
 327  
 328                  // Avoid the array_slice() if possible.
 329                  if ( 0 === $the_['accepted_args'] ) {
 330                      $value = call_user_func( $the_['function'] );
 331                  } elseif ( $the_['accepted_args'] >= $num_args ) {
 332                      $value = call_user_func_array( $the_['function'], $args );
 333                  } else {
 334                      $value = call_user_func_array( $the_['function'], array_slice( $args, 0, $the_['accepted_args'] ) );
 335                  }
 336              }
 337          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 338  
 339          unset( $this->iterations[ $nesting_level ] );
 340          unset( $this->current_priority[ $nesting_level ] );
 341  
 342          --$this->nesting_level;
 343  
 344          return $value;
 345      }
 346  
 347      /**
 348       * Calls the callback functions that have been added to an action hook.
 349       *
 350       * @since 4.7.0
 351       *
 352       * @param array $args Parameters to pass to the callback functions.
 353       */
 354  	public function do_action( $args ) {
 355          $this->doing_action = true;
 356          $this->apply_filters( '', $args );
 357  
 358          // If there are recursive calls to the current action, we haven't finished it until we get to the last one.
 359          if ( ! $this->nesting_level ) {
 360              $this->doing_action = false;
 361          }
 362      }
 363  
 364      /**
 365       * Processes the functions hooked into the 'all' hook.
 366       *
 367       * @since 4.7.0
 368       *
 369       * @param array $args Arguments to pass to the hook callbacks. Passed by reference.
 370       */
 371  	public function do_all_hook( &$args ) {
 372          $nesting_level                      = $this->nesting_level++;
 373          $this->iterations[ $nesting_level ] = $this->priorities;
 374  
 375          do {
 376              $priority = current( $this->iterations[ $nesting_level ] );
 377  
 378              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 379                  call_user_func_array( $the_['function'], $args );
 380              }
 381          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 382  
 383          unset( $this->iterations[ $nesting_level ] );
 384          --$this->nesting_level;
 385      }
 386  
 387      /**
 388       * Return the current priority level of the currently running iteration of the hook.
 389       *
 390       * @since 4.7.0
 391       *
 392       * @return int|false If the hook is running, return the current priority level.
 393       *                   If it isn't running, return false.
 394       */
 395  	public function current_priority() {
 396          if ( false === current( $this->iterations ) ) {
 397              return false;
 398          }
 399  
 400          return current( current( $this->iterations ) );
 401      }
 402  
 403      /**
 404       * Normalizes filters set up before WordPress has initialized to WP_Hook objects.
 405       *
 406       * The `$filters` parameter should be an array keyed by hook name, with values
 407       * containing either:
 408       *
 409       *  - A `WP_Hook` instance
 410       *  - An array of callbacks keyed by their priorities
 411       *
 412       * Examples:
 413       *
 414       *     $filters = array(
 415       *         'wp_fatal_error_handler_enabled' => array(
 416       *             10 => array(
 417       *                 array(
 418       *                     'accepted_args' => 0,
 419       *                     'function'      => function() {
 420       *                         return false;
 421       *                     },
 422       *                 ),
 423       *             ),
 424       *         ),
 425       *     );
 426       *
 427       * @since 4.7.0
 428       *
 429       * @param array $filters Filters to normalize. See documentation above for details.
 430       * @return WP_Hook[] Array of normalized filters.
 431       */
 432  	public static function build_preinitialized_hooks( $filters ) {
 433          /** @var WP_Hook[] $normalized */
 434          $normalized = array();
 435  
 436          foreach ( $filters as $hook_name => $callback_groups ) {
 437              if ( $callback_groups instanceof WP_Hook ) {
 438                  $normalized[ $hook_name ] = $callback_groups;
 439                  continue;
 440              }
 441  
 442              $hook = new WP_Hook();
 443  
 444              // Loop through callback groups.
 445              foreach ( $callback_groups as $priority => $callbacks ) {
 446  
 447                  // Loop through callbacks.
 448                  foreach ( $callbacks as $cb ) {
 449                      $hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
 450                  }
 451              }
 452  
 453              $normalized[ $hook_name ] = $hook;
 454          }
 455  
 456          return $normalized;
 457      }
 458  
 459      /**
 460       * Determines whether an offset value exists.
 461       *
 462       * @since 4.7.0
 463       *
 464       * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
 465       *
 466       * @param mixed $offset An offset to check for.
 467       * @return bool True if the offset exists, false otherwise.
 468       */
 469      #[ReturnTypeWillChange]
 470  	public function offsetExists( $offset ) {
 471          return isset( $this->callbacks[ $offset ] );
 472      }
 473  
 474      /**
 475       * Retrieves a value at a specified offset.
 476       *
 477       * @since 4.7.0
 478       *
 479       * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
 480       *
 481       * @param mixed $offset The offset to retrieve.
 482       * @return mixed If set, the value at the specified offset, null otherwise.
 483       */
 484      #[ReturnTypeWillChange]
 485  	public function offsetGet( $offset ) {
 486          return isset( $this->callbacks[ $offset ] ) ? $this->callbacks[ $offset ] : null;
 487      }
 488  
 489      /**
 490       * Sets a value at a specified offset.
 491       *
 492       * @since 4.7.0
 493       *
 494       * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
 495       *
 496       * @param mixed $offset The offset to assign the value to.
 497       * @param mixed $value The value to set.
 498       */
 499      #[ReturnTypeWillChange]
 500  	public function offsetSet( $offset, $value ) {
 501          if ( is_null( $offset ) ) {
 502              $this->callbacks[] = $value;
 503          } else {
 504              $this->callbacks[ $offset ] = $value;
 505          }
 506  
 507          $this->priorities = array_keys( $this->callbacks );
 508      }
 509  
 510      /**
 511       * Unsets a specified offset.
 512       *
 513       * @since 4.7.0
 514       *
 515       * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
 516       *
 517       * @param mixed $offset The offset to unset.
 518       */
 519      #[ReturnTypeWillChange]
 520  	public function offsetUnset( $offset ) {
 521          unset( $this->callbacks[ $offset ] );
 522          $this->priorities = array_keys( $this->callbacks );
 523      }
 524  
 525      /**
 526       * Returns the current element.
 527       *
 528       * @since 4.7.0
 529       *
 530       * @link https://www.php.net/manual/en/iterator.current.php
 531       *
 532       * @return array Of callbacks at current priority.
 533       */
 534      #[ReturnTypeWillChange]
 535  	public function current() {
 536          return current( $this->callbacks );
 537      }
 538  
 539      /**
 540       * Moves forward to the next element.
 541       *
 542       * @since 4.7.0
 543       *
 544       * @link https://www.php.net/manual/en/iterator.next.php
 545       *
 546       * @return array Of callbacks at next priority.
 547       */
 548      #[ReturnTypeWillChange]
 549  	public function next() {
 550          return next( $this->callbacks );
 551      }
 552  
 553      /**
 554       * Returns the key of the current element.
 555       *
 556       * @since 4.7.0
 557       *
 558       * @link https://www.php.net/manual/en/iterator.key.php
 559       *
 560       * @return mixed Returns current priority on success, or NULL on failure
 561       */
 562      #[ReturnTypeWillChange]
 563  	public function key() {
 564          return key( $this->callbacks );
 565      }
 566  
 567      /**
 568       * Checks if current position is valid.
 569       *
 570       * @since 4.7.0
 571       *
 572       * @link https://www.php.net/manual/en/iterator.valid.php
 573       *
 574       * @return bool Whether the current position is valid.
 575       */
 576      #[ReturnTypeWillChange]
 577  	public function valid() {
 578          return key( $this->callbacks ) !== null;
 579      }
 580  
 581      /**
 582       * Rewinds the Iterator to the first element.
 583       *
 584       * @since 4.7.0
 585       *
 586       * @link https://www.php.net/manual/en/iterator.rewind.php
 587       */
 588      #[ReturnTypeWillChange]
 589  	public function rewind() {
 590          reset( $this->callbacks );
 591      }
 592  }