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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   * @phpstan-type Hook_Callback array{
  19   *   function: callable,
  20   *   accepted_args: int,
  21   * }
  22   *
  23   * @phpstan-implements Iterator<int, array<non-decimal-int-string, Hook_Callback>>
  24   * @phpstan-implements ArrayAccess<int, array<non-decimal-int-string, Hook_Callback>>
  25   */
  26  #[AllowDynamicProperties]
  27  final class WP_Hook implements Iterator, ArrayAccess {
  28  
  29      /**
  30       * Hook callbacks keyed by priority.
  31       *
  32       * @since 4.7.0
  33       * @var array
  34       * @phpstan-var array<int, array<non-decimal-int-string, Hook_Callback>>
  35       */
  36      public $callbacks = array();
  37  
  38      /**
  39       * Priorities list.
  40       *
  41       * @since 6.4.0
  42       * @var list<int>
  43       */
  44      protected $priorities = array();
  45  
  46      /**
  47       * The priority keys of actively running iterations of a hook.
  48       *
  49       * @since 4.7.0
  50       * @var array<int, list<int>>
  51       */
  52      private $iterations = array();
  53  
  54      /**
  55       * The current priority of actively running iterations of a hook.
  56       *
  57       * @since 4.7.0
  58       * @var array<int, int>
  59       */
  60      private $current_priority = array();
  61  
  62      /**
  63       * Number of levels this hook can be recursively called.
  64       *
  65       * @since 4.7.0
  66       * @var int
  67       */
  68      private $nesting_level = 0;
  69  
  70      /**
  71       * Flag for if we're currently doing an action, rather than a filter.
  72       *
  73       * @since 4.7.0
  74       * @var bool
  75       */
  76      private $doing_action = false;
  77  
  78      /**
  79       * Adds a callback function to a filter hook.
  80       *
  81       * @since 4.7.0
  82       *
  83       * @param string   $hook_name     The name of the filter to add the callback to.
  84       * @param callable $callback      The callback to be run when the filter is applied.
  85       * @param int      $priority      The order in which the functions associated with a particular filter
  86       *                                are executed. Lower numbers correspond with earlier execution,
  87       *                                and functions with the same priority are executed in the order
  88       *                                in which they were added to the filter.
  89       * @param int      $accepted_args The number of arguments the function accepts.
  90       */
  91  	public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
  92          if ( null === $priority ) {
  93              $priority = 0;
  94          }
  95  
  96          $idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
  97          if ( null === $idx ) {
  98              return;
  99          }
 100  
 101          $priority_existed = isset( $this->callbacks[ $priority ] );
 102  
 103          $this->callbacks[ $priority ][ $idx ] = array(
 104              'function'      => $callback,
 105              'accepted_args' => (int) $accepted_args,
 106          );
 107  
 108          // If we're adding a new priority to the list, put them back in sorted order.
 109          if ( ! $priority_existed && count( $this->callbacks ) > 1 ) {
 110              ksort( $this->callbacks, SORT_NUMERIC );
 111          }
 112  
 113          $this->priorities = array_keys( $this->callbacks );
 114  
 115          if ( $this->nesting_level > 0 ) {
 116              $this->resort_active_iterations( $priority, $priority_existed );
 117          }
 118      }
 119  
 120      /**
 121       * Handles resetting callback priority keys mid-iteration.
 122       *
 123       * @since 4.7.0
 124       *
 125       * @param false|int $new_priority     Optional. The priority of the new filter being added. Default false,
 126       *                                    for no priority being added.
 127       * @param bool      $priority_existed Optional. Flag for whether the priority already existed before the new
 128       *                                    filter was added. Default false.
 129       */
 130  	private function resort_active_iterations( $new_priority = false, $priority_existed = false ) {
 131          $new_priorities = $this->priorities;
 132  
 133          // If there are no remaining hooks, clear out all running iterations.
 134          if ( ! $new_priorities ) {
 135              foreach ( $this->iterations as $index => $iteration ) {
 136                  $this->iterations[ $index ] = $new_priorities;
 137              }
 138  
 139              return;
 140          }
 141  
 142          $min = min( $new_priorities );
 143  
 144          foreach ( $this->iterations as $index => &$iteration ) {
 145              $current = current( $iteration );
 146  
 147              // If we're already at the end of this iteration, just leave the array pointer where it is.
 148              if ( false === $current ) {
 149                  continue;
 150              }
 151  
 152              $iteration = $new_priorities;
 153  
 154              if ( $current < $min ) {
 155                  array_unshift( $iteration, $current );
 156                  continue;
 157              }
 158  
 159              while ( current( $iteration ) < $current ) {
 160                  if ( false === next( $iteration ) ) {
 161                      break;
 162                  }
 163              }
 164  
 165              // If we have a new priority that didn't exist, but ::apply_filters() or ::do_action() thinks it's the current priority...
 166              if ( $new_priority === $this->current_priority[ $index ] && ! $priority_existed ) {
 167                  /*
 168                   * ...and the new priority is the same as what $this->iterations thinks is the previous
 169                   * priority, we need to move back to it.
 170                   */
 171  
 172                  if ( false === current( $iteration ) ) {
 173                      // If we've already moved off the end of the array, go back to the last element.
 174                      $prev = end( $iteration );
 175                  } else {
 176                      // Otherwise, just go back to the previous element.
 177                      $prev = prev( $iteration );
 178                  }
 179  
 180                  if ( false === $prev ) {
 181                      // Start of the array. Reset, and go about our day.
 182                      reset( $iteration );
 183                  } elseif ( $new_priority !== $prev ) {
 184                      // Previous wasn't the same. Move forward again.
 185                      next( $iteration );
 186                  }
 187              }
 188          }
 189  
 190          unset( $iteration );
 191      }
 192  
 193      /**
 194       * Removes a callback function from a filter hook.
 195       *
 196       * @since 4.7.0
 197       *
 198       * @param string                $hook_name The filter hook to which the function to be removed is hooked.
 199       * @param callable|string|array $callback  The callback to be removed from running when the filter is applied.
 200       *                                         This method can be called unconditionally to speculatively remove
 201       *                                         a callback that may or may not exist.
 202       * @param int                   $priority  The exact priority used when adding the original filter callback.
 203       * @return bool Whether the callback existed before it was removed.
 204       * @phpstan-param Maybe_Callable $callback
 205       */
 206  	public function remove_filter( $hook_name, $callback, $priority ) {
 207          if ( null === $priority ) {
 208              $priority = 0;
 209          }
 210  
 211          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
 212  
 213          $exists = isset( $function_key, $this->callbacks[ $priority ][ $function_key ] );
 214  
 215          if ( $exists ) {
 216              unset( $this->callbacks[ $priority ][ $function_key ] );
 217  
 218              if ( ! $this->callbacks[ $priority ] ) {
 219                  unset( $this->callbacks[ $priority ] );
 220  
 221                  $this->priorities = array_keys( $this->callbacks );
 222  
 223                  if ( $this->nesting_level > 0 ) {
 224                      $this->resort_active_iterations();
 225                  }
 226              }
 227          }
 228  
 229          return $exists;
 230      }
 231  
 232      /**
 233       * Checks if a specific callback has been registered for this hook.
 234       *
 235       * When using the `$callback` argument, this function may return a non-boolean value
 236       * that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
 237       *
 238       * @since 4.7.0
 239       * @since 6.9.0 Added the `$priority` parameter.
 240       *
 241       * @param string                      $hook_name Optional. The name of the filter hook. Default empty.
 242       * @param callable|string|array|false $callback  Optional. The callback to check for.
 243       *                                               This method can be called unconditionally to speculatively check
 244       *                                               a callback that may or may not exist. Default false.
 245       * @param int|false                   $priority  Optional. The specific priority at which to check for the callback.
 246       *                                               Default false.
 247       * @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
 248       *                  anything registered. When checking a specific function, the priority
 249       *                  of that hook is returned, or false if the function is not attached.
 250       *                  If `$callback` and `$priority` are both provided, a boolean is returned
 251       *                  for whether the specific function is registered at that priority.
 252       * @phpstan-param Maybe_Callable|false $callback
 253       */
 254  	public function has_filter( $hook_name = '', $callback = false, $priority = false ) {
 255          if ( false === $callback ) {
 256              return $this->has_filters();
 257          }
 258  
 259          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, is_int( $priority ) ? $priority : 10 );
 260  
 261          if ( ! $function_key ) {
 262              return false;
 263          }
 264  
 265          if ( is_int( $priority ) ) {
 266              return isset( $this->callbacks[ $priority ][ $function_key ] );
 267          }
 268  
 269          foreach ( $this->callbacks as $callback_priority => $callbacks ) {
 270              if ( isset( $callbacks[ $function_key ] ) ) {
 271                  return $callback_priority;
 272              }
 273          }
 274  
 275          return false;
 276      }
 277  
 278      /**
 279       * Checks if any callbacks have been registered for this hook.
 280       *
 281       * @since 4.7.0
 282       *
 283       * @return bool True if callbacks have been registered for the current hook, otherwise false.
 284       */
 285  	public function has_filters() {
 286          foreach ( $this->callbacks as $callbacks ) {
 287              if ( $callbacks ) {
 288                  return true;
 289              }
 290          }
 291  
 292          return false;
 293      }
 294  
 295      /**
 296       * Removes all callbacks from the current filter.
 297       *
 298       * @since 4.7.0
 299       *
 300       * @param int|false $priority Optional. The priority number to remove. Default false.
 301       */
 302  	public function remove_all_filters( $priority = false ) {
 303          if ( ! $this->callbacks ) {
 304              return;
 305          }
 306  
 307          if ( false === $priority ) {
 308              $this->callbacks  = array();
 309              $this->priorities = array();
 310          } elseif ( isset( $this->callbacks[ $priority ] ) ) {
 311              unset( $this->callbacks[ $priority ] );
 312              $this->priorities = array_keys( $this->callbacks );
 313          }
 314  
 315          if ( $this->nesting_level > 0 ) {
 316              $this->resort_active_iterations();
 317          }
 318      }
 319  
 320      /**
 321       * Calls the callback functions that have been added to a filter hook.
 322       *
 323       * @since 4.7.0
 324       *
 325       * @param mixed       $value The value to filter.
 326       * @param list<mixed> $args  Additional parameters to pass to the callback functions.
 327       *                           When filtering, this array is expected to include $value
 328       *                           at index 0. When called for an action by WP_Hook::do_action(),
 329       *                           it contains only the action arguments.
 330       * @return mixed The filtered value after all hooked functions are applied to it.
 331       */
 332  	public function apply_filters( $value, $args ) {
 333          if ( ! $this->callbacks ) {
 334              return $value;
 335          }
 336  
 337          $nesting_level = $this->nesting_level++;
 338  
 339          $this->iterations[ $nesting_level ] = $this->priorities;
 340  
 341          $num_args = count( $args );
 342  
 343          do {
 344              $priority = current( $this->iterations[ $nesting_level ] );
 345  
 346              if ( false === $priority ) {
 347                  // This is not expected to occur since the hook is known to have callbacks at one or more priorities.
 348                  break;
 349              }
 350  
 351              $this->current_priority[ $nesting_level ] = $priority;
 352  
 353              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 354                  if ( ! $this->doing_action ) {
 355                      $args[0] = $value;
 356                  }
 357  
 358                  // Avoid the array_slice() if possible.
 359                  if ( 0 === $the_['accepted_args'] ) {
 360                      $value = call_user_func( $the_['function'] );
 361                  } elseif ( $the_['accepted_args'] >= $num_args ) {
 362                      $value = call_user_func_array( $the_['function'], $args );
 363                  } else {
 364                      $value = call_user_func_array( $the_['function'], array_slice( $args, 0, $the_['accepted_args'] ) );
 365                  }
 366              }
 367          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 368  
 369          unset( $this->iterations[ $nesting_level ] );
 370          unset( $this->current_priority[ $nesting_level ] );
 371  
 372          --$this->nesting_level;
 373  
 374          return $value;
 375      }
 376  
 377      /**
 378       * Calls the callback functions that have been added to an action hook.
 379       *
 380       * @since 4.7.0
 381       *
 382       * @param list<mixed> $args Parameters to pass to the callback functions.
 383       */
 384  	public function do_action( $args ) {
 385          $this->doing_action = true;
 386          $this->apply_filters( '', $args );
 387  
 388          // If there are recursive calls to the current action, we haven't finished it until we get to the last one.
 389          if ( ! $this->nesting_level ) {
 390              $this->doing_action = false;
 391          }
 392      }
 393  
 394      /**
 395       * Processes the functions hooked into the 'all' hook.
 396       *
 397       * @since 4.7.0
 398       *
 399       * @param list<mixed> $args Arguments to pass to the hook callbacks. Passed by reference.
 400       */
 401  	public function do_all_hook( &$args ) {
 402          $nesting_level                      = $this->nesting_level++;
 403          $this->iterations[ $nesting_level ] = $this->priorities;
 404  
 405          do {
 406              $priority = current( $this->iterations[ $nesting_level ] );
 407  
 408              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 409                  call_user_func_array( $the_['function'], $args );
 410              }
 411          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 412  
 413          unset( $this->iterations[ $nesting_level ] );
 414          --$this->nesting_level;
 415      }
 416  
 417      /**
 418       * Return the current priority level of the currently running iteration of the hook.
 419       *
 420       * @since 4.7.0
 421       *
 422       * @return int|false If the hook is running, return the current priority level.
 423       *                   If it isn't running, return false.
 424       */
 425  	public function current_priority() {
 426          if ( false === current( $this->iterations ) ) {
 427              return false;
 428          }
 429  
 430          return current( current( $this->iterations ) );
 431      }
 432  
 433      /**
 434       * Normalizes filters set up before WordPress has initialized to WP_Hook objects.
 435       *
 436       * The `$filters` parameter should be an array keyed by hook name, with values
 437       * containing either:
 438       *
 439       *  - A `WP_Hook` instance
 440       *  - An array of callbacks keyed by their priorities
 441       *
 442       * Examples:
 443       *
 444       *     $filters = array(
 445       *         'wp_fatal_error_handler_enabled' => array(
 446       *             10 => array(
 447       *                 array(
 448       *                     'accepted_args' => 0,
 449       *                     'function'      => function() {
 450       *                         return false;
 451       *                     },
 452       *                 ),
 453       *             ),
 454       *         ),
 455       *     );
 456       *
 457       * @since 4.7.0
 458       *
 459       * @param array $filters Filters to normalize. See documentation above for details.
 460       * @phpstan-param array<string, WP_Hook|array<int, array<Hook_Callback>>> $filters
 461       * @return array<string, WP_Hook> Array of normalized filters keyed by hook name.
 462       */
 463  	public static function build_preinitialized_hooks( $filters ) {
 464          /** @var array<string, WP_Hook> $normalized */
 465          $normalized = array();
 466  
 467          foreach ( $filters as $hook_name => $callback_groups ) {
 468              if ( $callback_groups instanceof WP_Hook ) {
 469                  $normalized[ $hook_name ] = $callback_groups;
 470                  continue;
 471              }
 472  
 473              $hook = new WP_Hook();
 474  
 475              // Loop through callback groups.
 476              foreach ( $callback_groups as $priority => $callbacks ) {
 477  
 478                  // Loop through callbacks.
 479                  foreach ( $callbacks as $cb ) {
 480                      $hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
 481                  }
 482              }
 483  
 484              $normalized[ $hook_name ] = $hook;
 485          }
 486  
 487          return $normalized;
 488      }
 489  
 490      /**
 491       * Determines whether an offset value exists.
 492       *
 493       * @since 4.7.0
 494       *
 495       * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
 496       *
 497       * @param int $offset An offset to check for.
 498       * @return bool True if the offset exists, false otherwise.
 499       */
 500      #[ReturnTypeWillChange]
 501  	public function offsetExists( $offset ) {
 502          return isset( $this->callbacks[ $offset ] );
 503      }
 504  
 505      /**
 506       * Retrieves a value at a specified offset.
 507       *
 508       * @since 4.7.0
 509       *
 510       * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
 511       *
 512       * @param int $offset The offset to retrieve.
 513       * @return array|null If set, the value at the specified offset, null otherwise.
 514       * @phpstan-return array<non-decimal-int-string, Hook_Callback>|null
 515       */
 516      #[ReturnTypeWillChange]
 517  	public function offsetGet( $offset ) {
 518          return $this->callbacks[ $offset ] ?? null;
 519      }
 520  
 521      /**
 522       * Sets a value at a specified offset.
 523       *
 524       * @since 4.7.0
 525       *
 526       * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
 527       *
 528       * @param int|null $offset The offset to assign the value to.
 529       * @param array    $value  The value to set.
 530       * @phpstan-param array<non-decimal-int-string, Hook_Callback> $value
 531       */
 532      #[ReturnTypeWillChange]
 533  	public function offsetSet( $offset, $value ) {
 534          if ( is_null( $offset ) ) {
 535              $this->callbacks[] = $value;
 536          } else {
 537              $this->callbacks[ $offset ] = $value;
 538          }
 539  
 540          $this->priorities = array_keys( $this->callbacks );
 541      }
 542  
 543      /**
 544       * Unsets a specified offset.
 545       *
 546       * @since 4.7.0
 547       *
 548       * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
 549       *
 550       * @param int $offset The offset to unset.
 551       */
 552      #[ReturnTypeWillChange]
 553  	public function offsetUnset( $offset ) {
 554          unset( $this->callbacks[ $offset ] );
 555          $this->priorities = array_keys( $this->callbacks );
 556      }
 557  
 558      /**
 559       * Returns the current element.
 560       *
 561       * @since 4.7.0
 562       *
 563       * @link https://www.php.net/manual/en/iterator.current.php
 564       *
 565       * @return array|false Array of callbacks at current priority, false if there are no more elements.
 566       * @phpstan-return array<non-decimal-int-string, Hook_Callback>|false
 567       */
 568      #[ReturnTypeWillChange]
 569  	public function current() {
 570          return current( $this->callbacks );
 571      }
 572  
 573      /**
 574       * Moves forward to the next element.
 575       *
 576       * @since 4.7.0
 577       *
 578       * @link https://www.php.net/manual/en/iterator.next.php
 579       *
 580       * @return array|false Array of callbacks at next priority, false if there are no more elements.
 581       * @phpstan-return array<non-decimal-int-string, Hook_Callback>|false
 582       */
 583      #[ReturnTypeWillChange]
 584  	public function next() {
 585          return next( $this->callbacks );
 586      }
 587  
 588      /**
 589       * Returns the key of the current element.
 590       *
 591       * @since 4.7.0
 592       *
 593       * @link https://www.php.net/manual/en/iterator.key.php
 594       *
 595       * @return int|null Returns current priority on success, or NULL on failure
 596       */
 597      #[ReturnTypeWillChange]
 598  	public function key() {
 599          return key( $this->callbacks );
 600      }
 601  
 602      /**
 603       * Checks if current position is valid.
 604       *
 605       * @since 4.7.0
 606       *
 607       * @link https://www.php.net/manual/en/iterator.valid.php
 608       *
 609       * @return bool Whether the current position is valid.
 610       */
 611      #[ReturnTypeWillChange]
 612  	public function valid() {
 613          return key( $this->callbacks ) !== null;
 614      }
 615  
 616      /**
 617       * Rewinds the Iterator to the first element.
 618       *
 619       * @since 4.7.0
 620       *
 621       * @link https://www.php.net/manual/en/iterator.rewind.php
 622       */
 623      #[ReturnTypeWillChange]
 624  	public function rewind() {
 625          reset( $this->callbacks );
 626      }
 627  }