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/wp-includes/ -> class-wp-hook.php (source)

   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 $callback  The callback to be removed from running when the filter is applied.
 173       * @param int      $priority  The exact priority used when adding the original filter callback.
 174       * @return bool Whether the callback existed before it was removed.
 175       */
 176  	public function remove_filter( $hook_name, $callback, $priority ) {
 177          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
 178  
 179          $exists = isset( $this->callbacks[ $priority ][ $function_key ] );
 180  
 181          if ( $exists ) {
 182              unset( $this->callbacks[ $priority ][ $function_key ] );
 183  
 184              if ( ! $this->callbacks[ $priority ] ) {
 185                  unset( $this->callbacks[ $priority ] );
 186  
 187                  if ( $this->nesting_level > 0 ) {
 188                      $this->resort_active_iterations();
 189                  }
 190              }
 191          }
 192  
 193          return $exists;
 194      }
 195  
 196      /**
 197       * Checks if a specific callback has been registered for this hook.
 198       *
 199       * When using the `$callback` argument, this function may return a non-boolean value
 200       * that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.
 201       *
 202       * @since 4.7.0
 203       *
 204       * @param string         $hook_name Optional. The name of the filter hook. Default empty.
 205       * @param callable|false $callback  Optional. The callback to check for. Default false.
 206       * @return bool|int If `$callback` is omitted, returns boolean for whether the hook has
 207       *                  anything registered. When checking a specific function, the priority
 208       *                  of that hook is returned, or false if the function is not attached.
 209       */
 210  	public function has_filter( $hook_name = '', $callback = false ) {
 211          if ( false === $callback ) {
 212              return $this->has_filters();
 213          }
 214  
 215          $function_key = _wp_filter_build_unique_id( $hook_name, $callback, false );
 216  
 217          if ( ! $function_key ) {
 218              return false;
 219          }
 220  
 221          foreach ( $this->callbacks as $priority => $callbacks ) {
 222              if ( isset( $callbacks[ $function_key ] ) ) {
 223                  return $priority;
 224              }
 225          }
 226  
 227          return false;
 228      }
 229  
 230      /**
 231       * Checks if any callbacks have been registered for this hook.
 232       *
 233       * @since 4.7.0
 234       *
 235       * @return bool True if callbacks have been registered for the current hook, otherwise false.
 236       */
 237  	public function has_filters() {
 238          foreach ( $this->callbacks as $callbacks ) {
 239              if ( $callbacks ) {
 240                  return true;
 241              }
 242          }
 243  
 244          return false;
 245      }
 246  
 247      /**
 248       * Removes all callbacks from the current filter.
 249       *
 250       * @since 4.7.0
 251       *
 252       * @param int|false $priority Optional. The priority number to remove. Default false.
 253       */
 254  	public function remove_all_filters( $priority = false ) {
 255          if ( ! $this->callbacks ) {
 256              return;
 257          }
 258  
 259          if ( false === $priority ) {
 260              $this->callbacks = array();
 261          } elseif ( isset( $this->callbacks[ $priority ] ) ) {
 262              unset( $this->callbacks[ $priority ] );
 263          }
 264  
 265          if ( $this->nesting_level > 0 ) {
 266              $this->resort_active_iterations();
 267          }
 268      }
 269  
 270      /**
 271       * Calls the callback functions that have been added to a filter hook.
 272       *
 273       * @since 4.7.0
 274       *
 275       * @param mixed $value The value to filter.
 276       * @param array $args  Additional parameters to pass to the callback functions.
 277       *                     This array is expected to include $value at index 0.
 278       * @return mixed The filtered value after all hooked functions are applied to it.
 279       */
 280  	public function apply_filters( $value, $args ) {
 281          if ( ! $this->callbacks ) {
 282              return $value;
 283          }
 284  
 285          $nesting_level = $this->nesting_level++;
 286  
 287          $this->iterations[ $nesting_level ] = array_keys( $this->callbacks );
 288          $num_args                           = count( $args );
 289  
 290          do {
 291              $this->current_priority[ $nesting_level ] = current( $this->iterations[ $nesting_level ] );
 292              $priority                                 = $this->current_priority[ $nesting_level ];
 293  
 294              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 295                  if ( ! $this->doing_action ) {
 296                      $args[0] = $value;
 297                  }
 298  
 299                  // Avoid the array_slice() if possible.
 300                  if ( 0 == $the_['accepted_args'] ) {
 301                      $value = call_user_func( $the_['function'] );
 302                  } elseif ( $the_['accepted_args'] >= $num_args ) {
 303                      $value = call_user_func_array( $the_['function'], $args );
 304                  } else {
 305                      $value = call_user_func_array( $the_['function'], array_slice( $args, 0, (int) $the_['accepted_args'] ) );
 306                  }
 307              }
 308          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 309  
 310          unset( $this->iterations[ $nesting_level ] );
 311          unset( $this->current_priority[ $nesting_level ] );
 312  
 313          $this->nesting_level--;
 314  
 315          return $value;
 316      }
 317  
 318      /**
 319       * Calls the callback functions that have been added to an action hook.
 320       *
 321       * @since 4.7.0
 322       *
 323       * @param array $args Parameters to pass to the callback functions.
 324       */
 325  	public function do_action( $args ) {
 326          $this->doing_action = true;
 327          $this->apply_filters( '', $args );
 328  
 329          // If there are recursive calls to the current action, we haven't finished it until we get to the last one.
 330          if ( ! $this->nesting_level ) {
 331              $this->doing_action = false;
 332          }
 333      }
 334  
 335      /**
 336       * Processes the functions hooked into the 'all' hook.
 337       *
 338       * @since 4.7.0
 339       *
 340       * @param array $args Arguments to pass to the hook callbacks. Passed by reference.
 341       */
 342  	public function do_all_hook( &$args ) {
 343          $nesting_level                      = $this->nesting_level++;
 344          $this->iterations[ $nesting_level ] = array_keys( $this->callbacks );
 345  
 346          do {
 347              $priority = current( $this->iterations[ $nesting_level ] );
 348  
 349              foreach ( $this->callbacks[ $priority ] as $the_ ) {
 350                  call_user_func_array( $the_['function'], $args );
 351              }
 352          } while ( false !== next( $this->iterations[ $nesting_level ] ) );
 353  
 354          unset( $this->iterations[ $nesting_level ] );
 355          $this->nesting_level--;
 356      }
 357  
 358      /**
 359       * Return the current priority level of the currently running iteration of the hook.
 360       *
 361       * @since 4.7.0
 362       *
 363       * @return int|false If the hook is running, return the current priority level.
 364       *                   If it isn't running, return false.
 365       */
 366  	public function current_priority() {
 367          if ( false === current( $this->iterations ) ) {
 368              return false;
 369          }
 370  
 371          return current( current( $this->iterations ) );
 372      }
 373  
 374      /**
 375       * Normalizes filters set up before WordPress has initialized to WP_Hook objects.
 376       *
 377       * The `$filters` parameter should be an array keyed by hook name, with values
 378       * containing either:
 379       *
 380       *  - A `WP_Hook` instance
 381       *  - An array of callbacks keyed by their priorities
 382       *
 383       * Examples:
 384       *
 385       *     $filters = array(
 386       *         'wp_fatal_error_handler_enabled' => array(
 387       *             10 => array(
 388       *                 array(
 389       *                     'accepted_args' => 0,
 390       *                     'function'      => function() {
 391       *                         return false;
 392       *                     },
 393       *                 ),
 394       *             ),
 395       *         ),
 396       *     );
 397       *
 398       * @since 4.7.0
 399       *
 400       * @param array $filters Filters to normalize. See documentation above for details.
 401       * @return WP_Hook[] Array of normalized filters.
 402       */
 403  	public static function build_preinitialized_hooks( $filters ) {
 404          /** @var WP_Hook[] $normalized */
 405          $normalized = array();
 406  
 407          foreach ( $filters as $hook_name => $callback_groups ) {
 408              if ( is_object( $callback_groups ) && $callback_groups instanceof WP_Hook ) {
 409                  $normalized[ $hook_name ] = $callback_groups;
 410                  continue;
 411              }
 412  
 413              $hook = new WP_Hook();
 414  
 415              // Loop through callback groups.
 416              foreach ( $callback_groups as $priority => $callbacks ) {
 417  
 418                  // Loop through callbacks.
 419                  foreach ( $callbacks as $cb ) {
 420                      $hook->add_filter( $hook_name, $cb['function'], $priority, $cb['accepted_args'] );
 421                  }
 422              }
 423  
 424              $normalized[ $hook_name ] = $hook;
 425          }
 426  
 427          return $normalized;
 428      }
 429  
 430      /**
 431       * Determines whether an offset value exists.
 432       *
 433       * @since 4.7.0
 434       *
 435       * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
 436       *
 437       * @param mixed $offset An offset to check for.
 438       * @return bool True if the offset exists, false otherwise.
 439       */
 440  	public function offsetExists( $offset ) {
 441          return isset( $this->callbacks[ $offset ] );
 442      }
 443  
 444      /**
 445       * Retrieves a value at a specified offset.
 446       *
 447       * @since 4.7.0
 448       *
 449       * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
 450       *
 451       * @param mixed $offset The offset to retrieve.
 452       * @return mixed If set, the value at the specified offset, null otherwise.
 453       */
 454  	public function offsetGet( $offset ) {
 455          return isset( $this->callbacks[ $offset ] ) ? $this->callbacks[ $offset ] : null;
 456      }
 457  
 458      /**
 459       * Sets a value at a specified offset.
 460       *
 461       * @since 4.7.0
 462       *
 463       * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
 464       *
 465       * @param mixed $offset The offset to assign the value to.
 466       * @param mixed $value The value to set.
 467       */
 468  	public function offsetSet( $offset, $value ) {
 469          if ( is_null( $offset ) ) {
 470              $this->callbacks[] = $value;
 471          } else {
 472              $this->callbacks[ $offset ] = $value;
 473          }
 474      }
 475  
 476      /**
 477       * Unsets a specified offset.
 478       *
 479       * @since 4.7.0
 480       *
 481       * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
 482       *
 483       * @param mixed $offset The offset to unset.
 484       */
 485  	public function offsetUnset( $offset ) {
 486          unset( $this->callbacks[ $offset ] );
 487      }
 488  
 489      /**
 490       * Returns the current element.
 491       *
 492       * @since 4.7.0
 493       *
 494       * @link https://www.php.net/manual/en/iterator.current.php
 495       *
 496       * @return array Of callbacks at current priority.
 497       */
 498  	public function current() {
 499          return current( $this->callbacks );
 500      }
 501  
 502      /**
 503       * Moves forward to the next element.
 504       *
 505       * @since 4.7.0
 506       *
 507       * @link https://www.php.net/manual/en/iterator.next.php
 508       *
 509       * @return array Of callbacks at next priority.
 510       */
 511  	public function next() {
 512          return next( $this->callbacks );
 513      }
 514  
 515      /**
 516       * Returns the key of the current element.
 517       *
 518       * @since 4.7.0
 519       *
 520       * @link https://www.php.net/manual/en/iterator.key.php
 521       *
 522       * @return mixed Returns current priority on success, or NULL on failure
 523       */
 524  	public function key() {
 525          return key( $this->callbacks );
 526      }
 527  
 528      /**
 529       * Checks if current position is valid.
 530       *
 531       * @since 4.7.0
 532       *
 533       * @link https://www.php.net/manual/en/iterator.valid.php
 534       *
 535       * @return bool Whether the current position is valid.
 536       */
 537  	public function valid() {
 538          return key( $this->callbacks ) !== null;
 539      }
 540  
 541      /**
 542       * Rewinds the Iterator to the first element.
 543       *
 544       * @since 4.7.0
 545       *
 546       * @link https://www.php.net/manual/en/iterator.rewind.php
 547       */
 548  	public function rewind() {
 549          reset( $this->callbacks );
 550      }
 551  
 552  }


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