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