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