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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       * @since 6.9.0 Added the `$priority` parameter.
 227       *
 228       * @param string                      $hook_name Optional. The name of the filter hook. Default empty.
 229       * @param callable|string|array|false $callback  Optional. The callback to check for.
 230       *                                               This method can be called unconditionally to speculatively check
 231       *                                               a callback that may or may not exist. Default false.
 232       * @param int|false                   $priority  Optional. The specific priority at which to check for the callback.
 233       *                                               Default false.
 234       * @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
 235       *                  anything registered. When checking a specific function, the priority
 236       *                  of that hook is returned, or false if the function is not attached.
 237       *                  If `$callback` and `$priority` are both provided, a boolean is returned
 238       *                  for whether the specific function is registered at that priority.
 239       */
 240  	public function has_filter( $hook_name = '', $callback = false, $priority = false ) {
 241          if ( false === $callback ) {
 242              return $this->has_filters();
 243          }
 244  
 245          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );
 246  
 247          if ( ! $function_key ) {
 248              return false;
 249          }
 250  
 251          if ( is_int( $priority ) ) {
 252              return isset( $this->callbacks[ $priority ][ $function_key ] );
 253          }
 254  
 255          foreach ( $this->callbacks as $callback_priority => $callbacks ) {
 256              if ( isset( $callbacks[ $function_key ] ) ) {
 257                  return $callback_priority;
 258              }
 259          }
 260  
 261          return false;
 262      }
 263  
 264      /**
 265       * Checks if any callbacks have been registered for this hook.
 266       *
 267       * @since 4.7.0
 268       *
 269       * @return bool True if callbacks have been registered for the current hook, otherwise false.
 270       */
 271  	public function has_filters() {
 272          foreach ( $this->callbacks as $callbacks ) {
 273              if ( $callbacks ) {
 274                  return true;
 275              }
 276          }
 277  
 278          return false;
 279      }
 280  
 281      /**
 282       * Removes all callbacks from the current filter.
 283       *
 284       * @since 4.7.0
 285       *
 286       * @param int|false $priority Optional. The priority number to remove. Default false.
 287       */
 288  	public function remove_all_filters( $priority = false ) {
 289          if ( ! $this->callbacks ) {
 290              return;
 291          }
 292  
 293          if ( false === $priority ) {
 294              $this->callbacks  = array();
 295              $this->priorities = array();
 296          } elseif ( isset( $this->callbacks[ $priority ] ) ) {
 297              unset( $this->callbacks[ $priority ] );
 298              $this->priorities = array_keys( $this->callbacks );
 299          }
 300  
 301          if ( $this->nesting_level > 0 ) {
 302              $this->resort_active_iterations();
 303          }
 304      }
 305  
 306      /**
 307       * Calls the callback functions that have been added to a filter hook.
 308       *
 309       * @since 4.7.0
 310       *
 311       * @param mixed $value The value to filter.
 312       * @param array $args  Additional parameters to pass to the callback functions.
 313       *                     This array is expected to include $value at index 0.
 314       * @return mixed The filtered value after all hooked functions are applied to it.
 315       */
 316  	public function apply_filters( $value, $args ) {
 317          if ( ! $this->callbacks ) {
 318              return $value;
 319          }
 320  
 321          $nesting_level = $this->nesting_level++;
 322  
 323          $this->iterations[ $nesting_level ] = $this->priorities;
 324  
 325          $num_args = count( $args );
 326  
 327          do {
 328              $this->current_priority[ $nesting_level ] = current( $this->iterations[ $nesting_level ] );
 329  
 330              $priority = $this->current_priority[ $nesting_level ];
 331  
 332              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 333                  if ( ! $this->doing_action ) {
 334                      $args[0] = $value;
 335                  }
 336  
 337                  // Avoid the array_slice() if possible.
 338                  if ( 0 === $the_['accepted_args'] ) {
 339                      $value = call_user_func( $the_['function'] );
 340                  } elseif ( $the_['accepted_args'] >= $num_args ) {
 341                      $value = call_user_func_array( $the_['function'], $args );
 342                  } else {
 343                      $value = call_user_func_array( $the_['function'], array_slice( $args, 0, $the_['accepted_args'] ) );
 344                  }
 345              }
 346          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 347  
 348          unset( $this->iterations[ $nesting_level ] );
 349          unset( $this->current_priority[ $nesting_level ] );
 350  
 351          --$this->nesting_level;
 352  
 353          return $value;
 354      }
 355  
 356      /**
 357       * Calls the callback functions that have been added to an action hook.
 358       *
 359       * @since 4.7.0
 360       *
 361       * @param array $args Parameters to pass to the callback functions.
 362       */
 363  	public function do_action( $args ) {
 364          $this->doing_action = true;
 365          $this->apply_filters( '', $args );
 366  
 367          // If there are recursive calls to the current action, we haven't finished it until we get to the last one.
 368          if ( ! $this->nesting_level ) {
 369              $this->doing_action = false;
 370          }
 371      }
 372  
 373      /**
 374       * Processes the functions hooked into the 'all' hook.
 375       *
 376       * @since 4.7.0
 377       *
 378       * @param array $args Arguments to pass to the hook callbacks. Passed by reference.
 379       */
 380  	public function do_all_hook( &$args ) {
 381          $nesting_level                      = $this->nesting_level++;
 382          $this->iterations[ $nesting_level ] = $this->priorities;
 383  
 384          do {
 385              $priority = current( $this->iterations[ $nesting_level ] );
 386  
 387              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 388                  call_user_func_array( $the_['function'], $args );
 389              }
 390          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 391  
 392          unset( $this->iterations[ $nesting_level ] );
 393          --$this->nesting_level;
 394      }
 395  
 396      /**
 397       * Return the current priority level of the currently running iteration of the hook.
 398       *
 399       * @since 4.7.0
 400       *
 401       * @return int|false If the hook is running, return the current priority level.
 402       *                   If it isn't running, return false.
 403       */
 404  	public function current_priority() {
 405          if ( false === current( $this->iterations ) ) {
 406              return false;
 407          }
 408  
 409          return current( current( $this->iterations ) );
 410      }
 411  
 412      /**
 413       * Normalizes filters set up before WordPress has initialized to WP_Hook objects.
 414       *
 415       * The `$filters` parameter should be an array keyed by hook name, with values
 416       * containing either:
 417       *
 418       *  - A `WP_Hook` instance
 419       *  - An array of callbacks keyed by their priorities
 420       *
 421       * Examples:
 422       *
 423       *     $filters = array(
 424       *         'wp_fatal_error_handler_enabled' => array(
 425       *             10 => array(
 426       *                 array(
 427       *                     'accepted_args' => 0,
 428       *                     'function'      => function() {
 429       *                         return false;
 430       *                     },
 431       *                 ),
 432       *             ),
 433       *         ),
 434       *     );
 435       *
 436       * @since 4.7.0
 437       *
 438       * @param array $filters Filters to normalize. See documentation above for details.
 439       * @return WP_Hook[] Array of normalized filters.
 440       */
 441  	public static function build_preinitialized_hooks( $filters ) {
 442          /** @var WP_Hook[] $normalized */
 443          $normalized = array();
 444  
 445          foreach ( $filters as $hook_name => $callback_groups ) {
 446              if ( $callback_groups instanceof WP_Hook ) {
 447                  $normalized[ $hook_name ] = $callback_groups;
 448                  continue;
 449              }
 450  
 451              $hook = new WP_Hook();
 452  
 453              // Loop through callback groups.
 454              foreach ( $callback_groups as $priority => $callbacks ) {
 455  
 456                  // Loop through callbacks.
 457                  foreach ( $callbacks as $cb ) {
 458                      $hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
 459                  }
 460              }
 461  
 462              $normalized[ $hook_name ] = $hook;
 463          }
 464  
 465          return $normalized;
 466      }
 467  
 468      /**
 469       * Determines whether an offset value exists.
 470       *
 471       * @since 4.7.0
 472       *
 473       * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
 474       *
 475       * @param mixed $offset An offset to check for.
 476       * @return bool True if the offset exists, false otherwise.
 477       */
 478      #[ReturnTypeWillChange]
 479  	public function offsetExists( $offset ) {
 480          return isset( $this->callbacks[ $offset ] );
 481      }
 482  
 483      /**
 484       * Retrieves a value at a specified offset.
 485       *
 486       * @since 4.7.0
 487       *
 488       * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
 489       *
 490       * @param mixed $offset The offset to retrieve.
 491       * @return mixed If set, the value at the specified offset, null otherwise.
 492       */
 493      #[ReturnTypeWillChange]
 494  	public function offsetGet( $offset ) {
 495          return $this->callbacks[ $offset ] ?? null;
 496      }
 497  
 498      /**
 499       * Sets a value at a specified offset.
 500       *
 501       * @since 4.7.0
 502       *
 503       * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
 504       *
 505       * @param mixed $offset The offset to assign the value to.
 506       * @param mixed $value The value to set.
 507       */
 508      #[ReturnTypeWillChange]
 509  	public function offsetSet( $offset, $value ) {
 510          if ( is_null( $offset ) ) {
 511              $this->callbacks[] = $value;
 512          } else {
 513              $this->callbacks[ $offset ] = $value;
 514          }
 515  
 516          $this->priorities = array_keys( $this->callbacks );
 517      }
 518  
 519      /**
 520       * Unsets a specified offset.
 521       *
 522       * @since 4.7.0
 523       *
 524       * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
 525       *
 526       * @param mixed $offset The offset to unset.
 527       */
 528      #[ReturnTypeWillChange]
 529  	public function offsetUnset( $offset ) {
 530          unset( $this->callbacks[ $offset ] );
 531          $this->priorities = array_keys( $this->callbacks );
 532      }
 533  
 534      /**
 535       * Returns the current element.
 536       *
 537       * @since 4.7.0
 538       *
 539       * @link https://www.php.net/manual/en/iterator.current.php
 540       *
 541       * @return array Of callbacks at current priority.
 542       */
 543      #[ReturnTypeWillChange]
 544  	public function current() {
 545          return current( $this->callbacks );
 546      }
 547  
 548      /**
 549       * Moves forward to the next element.
 550       *
 551       * @since 4.7.0
 552       *
 553       * @link https://www.php.net/manual/en/iterator.next.php
 554       *
 555       * @return array Of callbacks at next priority.
 556       */
 557      #[ReturnTypeWillChange]
 558  	public function next() {
 559          return next( $this->callbacks );
 560      }
 561  
 562      /**
 563       * Returns the key of the current element.
 564       *
 565       * @since 4.7.0
 566       *
 567       * @link https://www.php.net/manual/en/iterator.key.php
 568       *
 569       * @return mixed Returns current priority on success, or NULL on failure
 570       */
 571      #[ReturnTypeWillChange]
 572  	public function key() {
 573          return key( $this->callbacks );
 574      }
 575  
 576      /**
 577       * Checks if current position is valid.
 578       *
 579       * @since 4.7.0
 580       *
 581       * @link https://www.php.net/manual/en/iterator.valid.php
 582       *
 583       * @return bool Whether the current position is valid.
 584       */
 585      #[ReturnTypeWillChange]
 586  	public function valid() {
 587          return key( $this->callbacks ) !== null;
 588      }
 589  
 590      /**
 591       * Rewinds the Iterator to the first element.
 592       *
 593       * @since 4.7.0
 594       *
 595       * @link https://www.php.net/manual/en/iterator.rewind.php
 596       */
 597      #[ReturnTypeWillChange]
 598  	public function rewind() {
 599          reset( $this->callbacks );
 600      }
 601  }