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   1  <?php
   2  /**
   3   * The plugin API is located in this file, which allows for creating actions
   4   * and filters and hooking functions, and methods. The functions or methods will
   5   * then be run when the action or filter is called.
   6   *
   7   * The API callback examples reference functions, but can be methods of classes.
   8   * To hook methods, you'll need to pass an array one of two ways.
   9   *
  10   * Any of the syntaxes explained in the PHP documentation for the
  11   * {@link http://us2.php.net/manual/en/language.pseudo-types.php#language.types.callback 'callback'}
  12   * type are valid.
  13   *
  14   * Also see the {@link http://codex.wordpress.org/Plugin_API Plugin API} for
  15   * more information and examples on how to use a lot of these functions.
  16   *
  17   * @package WordPress
  18   * @subpackage Plugin
  19   * @since 1.5
  20   */
  21  
  22  /**
  23   * Hooks a function or method to a specific filter action.
  24   *
  25   * Filters are the hooks that WordPress launches to modify text of various types
  26   * before adding it to the database or sending it to the browser screen. Plugins
  27   * can specify that one or more of its PHP functions is executed to
  28   * modify specific types of text at these times, using the Filter API.
  29   *
  30   * To use the API, the following code should be used to bind a callback to the
  31   * filter.
  32   *
  33   * <code>
  34   * function example_hook($example) { echo $example; }
  35   * add_filter('example_filter', 'example_hook');
  36   * </code>
  37   *
  38   * In WordPress 1.5.1+, hooked functions can take extra arguments that are set
  39   * when the matching do_action() or apply_filters() call is run. The
  40   * $accepted_args allow for calling functions only when the number of args
  41   * match. Hooked functions can take extra arguments that are set when the
  42   * matching do_action() or apply_filters() call is run. For example, the action
  43   * comment_id_not_found will pass any functions that hook onto it the ID of the
  44   * requested comment.
  45   *
  46   * <strong>Note:</strong> the function will return true no matter if the
  47   * function was hooked fails or not. There are no checks for whether the
  48   * function exists beforehand and no checks to whether the <tt>$function_to_add
  49   * is even a string. It is up to you to take care and this is done for
  50   * optimization purposes, so everything is as quick as possible.
  51   *
  52   * @package WordPress
  53   * @subpackage Plugin
  54   * @since 0.71
  55   * @global array $wp_filter Stores all of the filters added in the form of
  56   *    wp_filter['tag']['array of priorities']['array of functions serialized']['array of ['array (functions, accepted_args)']']
  57   * @global array $merged_filters Tracks the tags that need to be merged for later. If the hook is added, it doesn't need to run through that process.
  58   *
  59   * @param string $tag The name of the filter to hook the $function_to_add to.
  60   * @param callback $function_to_add The name of the function to be called when the filter is applied.
  61   * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
  62   * @param int $accepted_args optional. The number of arguments the function accept (default 1).
  63   * @return boolean true
  64   */
  65  function add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
  66      global $wp_filter, $merged_filters;
  67  
  68      $idx = _wp_filter_build_unique_id($tag, $function_to_add, $priority);
  69      $wp_filter[$tag][$priority][$idx] = array('function' => $function_to_add, 'accepted_args' => $accepted_args);
  70      unset( $merged_filters[ $tag ] );
  71      return true;
  72  }
  73  
  74  /**
  75   * Check if any filter has been registered for a hook.
  76   *
  77   * @package WordPress
  78   * @subpackage Plugin
  79   * @since 2.5
  80   * @global array $wp_filter Stores all of the filters
  81   *
  82   * @param string $tag The name of the filter hook.
  83   * @param callback $function_to_check optional.  If specified, return the priority of that function on this hook or false if not attached.
  84   * @return int|boolean Optionally returns the priority on that hook for the specified function.
  85   */
  86  function has_filter($tag, $function_to_check = false) {
  87      global $wp_filter;
  88  
  89      $has = !empty($wp_filter[$tag]);
  90      if ( false === $function_to_check || false == $has )
  91          return $has;
  92  
  93      if ( !$idx = _wp_filter_build_unique_id($tag, $function_to_check, false) )
  94          return false;
  95  
  96      foreach ( (array) array_keys($wp_filter[$tag]) as $priority ) {
  97          if ( isset($wp_filter[$tag][$priority][$idx]) )
  98              return $priority;
  99      }
 100  
 101      return false;
 102  }
 103  
 104  /**
 105   * Call the functions added to a filter hook.
 106   *
 107   * The callback functions attached to filter hook $tag are invoked by calling
 108   * this function. This function can be used to create a new filter hook by
 109   * simply calling this function with the name of the new hook specified using
 110   * the $tag parameter.
 111   *
 112   * The function allows for additional arguments to be added and passed to hooks.
 113   * <code>
 114   * function example_hook($string, $arg1, $arg2)
 115   * {
 116   *        //Do stuff
 117   *        return $string;
 118   * }
 119   * $value = apply_filters('example_filter', 'filter me', 'arg1', 'arg2');
 120   * </code>
 121   *
 122   * @package WordPress
 123   * @subpackage Plugin
 124   * @since 0.71
 125   * @global array $wp_filter Stores all of the filters
 126   * @global array $merged_filters Merges the filter hooks using this function.
 127   * @global array $wp_current_filter stores the list of current filters with the current one last
 128   *
 129   * @param string $tag The name of the filter hook.
 130   * @param mixed $value The value on which the filters hooked to <tt>$tag</tt> are applied on.
 131   * @param mixed $var,... Additional variables passed to the functions hooked to <tt>$tag</tt>.
 132   * @return mixed The filtered value after all hooked functions are applied to it.
 133   */
 134  function apply_filters($tag, $value) {
 135      global $wp_filter, $merged_filters, $wp_current_filter;
 136  
 137      $args = array();
 138      $wp_current_filter[] = $tag;
 139  
 140      // Do 'all' actions first
 141      if ( isset($wp_filter['all']) ) {
 142          $args = func_get_args();
 143          _wp_call_all_hook($args);
 144      }
 145  
 146      if ( !isset($wp_filter[$tag]) ) {
 147          array_pop($wp_current_filter);
 148          return $value;
 149      }
 150  
 151      // Sort
 152      if ( !isset( $merged_filters[ $tag ] ) ) {
 153          ksort($wp_filter[$tag]);
 154          $merged_filters[ $tag ] = true;
 155      }
 156  
 157      reset( $wp_filter[ $tag ] );
 158  
 159      if ( empty($args) )
 160          $args = func_get_args();
 161  
 162      do {
 163          foreach( (array) current($wp_filter[$tag]) as $the_ )
 164              if ( !is_null($the_['function']) ){
 165                  $args[1] = $value;
 166                  $value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
 167              }
 168  
 169      } while ( next($wp_filter[$tag]) !== false );
 170  
 171      array_pop( $wp_current_filter );
 172  
 173      return $value;
 174  }
 175  
 176  /**
 177   * Execute functions hooked on a specific filter hook, specifying arguments in an array.
 178   *
 179   * @see apply_filters() This function is identical, but the arguments passed to the
 180   * functions hooked to <tt>$tag</tt> are supplied using an array.
 181   *
 182   * @package WordPress
 183   * @subpackage Plugin
 184   * @since 3.0.0
 185   * @global array $wp_filter Stores all of the filters
 186   * @global array $merged_filters Merges the filter hooks using this function.
 187   * @global array $wp_current_filter stores the list of current filters with the current one last
 188   *
 189   * @param string $tag The name of the filter hook.
 190   * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
 191   * @return mixed The filtered value after all hooked functions are applied to it.
 192   */
 193  function apply_filters_ref_array($tag, $args) {
 194      global $wp_filter, $merged_filters, $wp_current_filter;
 195  
 196      $wp_current_filter[] = $tag;
 197  
 198      // Do 'all' actions first
 199      if ( isset($wp_filter['all']) ) {
 200          $all_args = func_get_args();
 201          _wp_call_all_hook($all_args);
 202      }
 203  
 204      if ( !isset($wp_filter[$tag]) ) {
 205          array_pop($wp_current_filter);
 206          return $args[0];
 207      }
 208  
 209      // Sort
 210      if ( !isset( $merged_filters[ $tag ] ) ) {
 211          ksort($wp_filter[$tag]);
 212          $merged_filters[ $tag ] = true;
 213      }
 214  
 215      reset( $wp_filter[ $tag ] );
 216  
 217      do {
 218          foreach( (array) current($wp_filter[$tag]) as $the_ )
 219              if ( !is_null($the_['function']) )
 220                  $args[0] = call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
 221  
 222      } while ( next($wp_filter[$tag]) !== false );
 223  
 224      array_pop( $wp_current_filter );
 225  
 226      return $args[0];
 227  }
 228  
 229  /**
 230   * Removes a function from a specified filter hook.
 231   *
 232   * This function removes a function attached to a specified filter hook. This
 233   * method can be used to remove default functions attached to a specific filter
 234   * hook and possibly replace them with a substitute.
 235   *
 236   * To remove a hook, the $function_to_remove and $priority arguments must match
 237   * when the hook was added. This goes for both filters and actions. No warning
 238   * will be given on removal failure.
 239   *
 240   * @package WordPress
 241   * @subpackage Plugin
 242   * @since 1.2
 243   *
 244   * @param string $tag The filter hook to which the function to be removed is hooked.
 245   * @param callback $function_to_remove The name of the function which should be removed.
 246   * @param int $priority optional. The priority of the function (default: 10).
 247   * @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
 248   * @return boolean Whether the function existed before it was removed.
 249   */
 250  function remove_filter($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
 251      $function_to_remove = _wp_filter_build_unique_id($tag, $function_to_remove, $priority);
 252  
 253      $r = isset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
 254  
 255      if ( true === $r) {
 256          unset($GLOBALS['wp_filter'][$tag][$priority][$function_to_remove]);
 257          if ( empty($GLOBALS['wp_filter'][$tag][$priority]) )
 258              unset($GLOBALS['wp_filter'][$tag][$priority]);
 259          unset($GLOBALS['merged_filters'][$tag]);
 260      }
 261  
 262      return $r;
 263  }
 264  
 265  /**
 266   * Remove all of the hooks from a filter.
 267   *
 268   * @since 2.7
 269   *
 270   * @param string $tag The filter to remove hooks from.
 271   * @param int $priority The priority number to remove.
 272   * @return bool True when finished.
 273   */
 274  function remove_all_filters($tag, $priority = false) {
 275      global $wp_filter, $merged_filters;
 276  
 277      if( isset($wp_filter[$tag]) ) {
 278          if( false !== $priority && isset($wp_filter[$tag][$priority]) )
 279              unset($wp_filter[$tag][$priority]);
 280          else
 281              unset($wp_filter[$tag]);
 282      }
 283  
 284      if( isset($merged_filters[$tag]) )
 285          unset($merged_filters[$tag]);
 286  
 287      return true;
 288  }
 289  
 290  /**
 291   * Retrieve the name of the current filter or action.
 292   *
 293   * @package WordPress
 294   * @subpackage Plugin
 295   * @since 2.5
 296   *
 297   * @return string Hook name of the current filter or action.
 298   */
 299  function current_filter() {
 300      global $wp_current_filter;
 301      return end( $wp_current_filter );
 302  }
 303  
 304  
 305  /**
 306   * Hooks a function on to a specific action.
 307   *
 308   * Actions are the hooks that the WordPress core launches at specific points
 309   * during execution, or when specific events occur. Plugins can specify that
 310   * one or more of its PHP functions are executed at these points, using the
 311   * Action API.
 312   *
 313   * @uses add_filter() Adds an action. Parameter list and functionality are the same.
 314   *
 315   * @package WordPress
 316   * @subpackage Plugin
 317   * @since 1.2
 318   *
 319   * @param string $tag The name of the action to which the $function_to_add is hooked.
 320   * @param callback $function_to_add The name of the function you wish to be called.
 321   * @param int $priority optional. Used to specify the order in which the functions associated with a particular action are executed (default: 10). Lower numbers correspond with earlier execution, and functions with the same priority are executed in the order in which they were added to the action.
 322   * @param int $accepted_args optional. The number of arguments the function accept (default 1).
 323   */
 324  function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
 325      return add_filter($tag, $function_to_add, $priority, $accepted_args);
 326  }
 327  
 328  
 329  /**
 330   * Execute functions hooked on a specific action hook.
 331   *
 332   * This function invokes all functions attached to action hook $tag. It is
 333   * possible to create new action hooks by simply calling this function,
 334   * specifying the name of the new hook using the <tt>$tag</tt> parameter.
 335   *
 336   * You can pass extra arguments to the hooks, much like you can with
 337   * apply_filters().
 338   *
 339   * @see apply_filters() This function works similar with the exception that
 340   * nothing is returned and only the functions or methods are called.
 341   *
 342   * @package WordPress
 343   * @subpackage Plugin
 344   * @since 1.2
 345   * @global array $wp_filter Stores all of the filters
 346   * @global array $wp_actions Increments the amount of times action was triggered.
 347   *
 348   * @param string $tag The name of the action to be executed.
 349   * @param mixed $arg,... Optional additional arguments which are passed on to the functions hooked to the action.
 350   * @return null Will return null if $tag does not exist in $wp_filter array
 351   */
 352  function do_action($tag, $arg = '') {
 353      global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
 354  
 355      if ( ! isset($wp_actions) )
 356          $wp_actions = array();
 357  
 358      if ( ! isset($wp_actions[$tag]) )
 359          $wp_actions[$tag] = 1;
 360      else
 361          ++$wp_actions[$tag];
 362  
 363      $wp_current_filter[] = $tag;
 364  
 365      // Do 'all' actions first
 366      if ( isset($wp_filter['all']) ) {
 367          $all_args = func_get_args();
 368          _wp_call_all_hook($all_args);
 369      }
 370  
 371      if ( !isset($wp_filter[$tag]) ) {
 372          array_pop($wp_current_filter);
 373          return;
 374      }
 375  
 376      $args = array();
 377      if ( is_array($arg) && 1 == count($arg) && isset($arg[0]) && is_object($arg[0]) ) // array(&$this)
 378          $args[] =& $arg[0];
 379      else
 380          $args[] = $arg;
 381      for ( $a = 2; $a < func_num_args(); $a++ )
 382          $args[] = func_get_arg($a);
 383  
 384      // Sort
 385      if ( !isset( $merged_filters[ $tag ] ) ) {
 386          ksort($wp_filter[$tag]);
 387          $merged_filters[ $tag ] = true;
 388      }
 389  
 390      reset( $wp_filter[ $tag ] );
 391  
 392      do {
 393          foreach ( (array) current($wp_filter[$tag]) as $the_ )
 394              if ( !is_null($the_['function']) )
 395                  call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
 396  
 397      } while ( next($wp_filter[$tag]) !== false );
 398  
 399      array_pop($wp_current_filter);
 400  }
 401  
 402  /**
 403   * Retrieve the number times an action is fired.
 404   *
 405   * @package WordPress
 406   * @subpackage Plugin
 407   * @since 2.1
 408   * @global array $wp_actions Increments the amount of times action was triggered.
 409   *
 410   * @param string $tag The name of the action hook.
 411   * @return int The number of times action hook <tt>$tag</tt> is fired
 412   */
 413  function did_action($tag) {
 414      global $wp_actions;
 415  
 416      if ( ! isset( $wp_actions ) || ! isset( $wp_actions[$tag] ) )
 417          return 0;
 418  
 419      return $wp_actions[$tag];
 420  }
 421  
 422  /**
 423   * Execute functions hooked on a specific action hook, specifying arguments in an array.
 424   *
 425   * @see do_action() This function is identical, but the arguments passed to the
 426   * functions hooked to <tt>$tag</tt> are supplied using an array.
 427   *
 428   * @package WordPress
 429   * @subpackage Plugin
 430   * @since 2.1
 431   * @global array $wp_filter Stores all of the filters
 432   * @global array $wp_actions Increments the amount of times action was triggered.
 433   *
 434   * @param string $tag The name of the action to be executed.
 435   * @param array $args The arguments supplied to the functions hooked to <tt>$tag</tt>
 436   * @return null Will return null if $tag does not exist in $wp_filter array
 437   */
 438  function do_action_ref_array($tag, $args) {
 439      global $wp_filter, $wp_actions, $merged_filters, $wp_current_filter;
 440  
 441      if ( ! isset($wp_actions) )
 442          $wp_actions = array();
 443  
 444      if ( ! isset($wp_actions[$tag]) )
 445          $wp_actions[$tag] = 1;
 446      else
 447          ++$wp_actions[$tag];
 448  
 449      $wp_current_filter[] = $tag;
 450  
 451      // Do 'all' actions first
 452      if ( isset($wp_filter['all']) ) {
 453          $all_args = func_get_args();
 454          _wp_call_all_hook($all_args);
 455      }
 456  
 457      if ( !isset($wp_filter[$tag]) ) {
 458          array_pop($wp_current_filter);
 459          return;
 460      }
 461  
 462      // Sort
 463      if ( !isset( $merged_filters[ $tag ] ) ) {
 464          ksort($wp_filter[$tag]);
 465          $merged_filters[ $tag ] = true;
 466      }
 467  
 468      reset( $wp_filter[ $tag ] );
 469  
 470      do {
 471          foreach( (array) current($wp_filter[$tag]) as $the_ )
 472              if ( !is_null($the_['function']) )
 473                  call_user_func_array($the_['function'], array_slice($args, 0, (int) $the_['accepted_args']));
 474  
 475      } while ( next($wp_filter[$tag]) !== false );
 476  
 477      array_pop($wp_current_filter);
 478  }
 479  
 480  /**
 481   * Check if any action has been registered for a hook.
 482   *
 483   * @package WordPress
 484   * @subpackage Plugin
 485   * @since 2.5
 486   * @see has_filter() has_action() is an alias of has_filter().
 487   *
 488   * @param string $tag The name of the action hook.
 489   * @param callback $function_to_check optional.  If specified, return the priority of that function on this hook or false if not attached.
 490   * @return int|boolean Optionally returns the priority on that hook for the specified function.
 491   */
 492  function has_action($tag, $function_to_check = false) {
 493      return has_filter($tag, $function_to_check);
 494  }
 495  
 496  /**
 497   * Removes a function from a specified action hook.
 498   *
 499   * This function removes a function attached to a specified action hook. This
 500   * method can be used to remove default functions attached to a specific filter
 501   * hook and possibly replace them with a substitute.
 502   *
 503   * @package WordPress
 504   * @subpackage Plugin
 505   * @since 1.2
 506   *
 507   * @param string $tag The action hook to which the function to be removed is hooked.
 508   * @param callback $function_to_remove The name of the function which should be removed.
 509   * @param int $priority optional The priority of the function (default: 10).
 510   * @param int $accepted_args optional. The number of arguments the function accpets (default: 1).
 511   * @return boolean Whether the function is removed.
 512   */
 513  function remove_action($tag, $function_to_remove, $priority = 10, $accepted_args = 1) {
 514      return remove_filter($tag, $function_to_remove, $priority, $accepted_args);
 515  }
 516  
 517  /**
 518   * Remove all of the hooks from an action.
 519   *
 520   * @since 2.7
 521   *
 522   * @param string $tag The action to remove hooks from.
 523   * @param int $priority The priority number to remove them from.
 524   * @return bool True when finished.
 525   */
 526  function remove_all_actions($tag, $priority = false) {
 527      return remove_all_filters($tag, $priority);
 528  }
 529  
 530  //
 531  // Functions for handling plugins.
 532  //
 533  
 534  /**
 535   * Gets the basename of a plugin.
 536   *
 537   * This method extracts the name of a plugin from its filename.
 538   *
 539   * @package WordPress
 540   * @subpackage Plugin
 541   * @since 1.5
 542   *
 543   * @access private
 544   *
 545   * @param string $file The filename of plugin.
 546   * @return string The name of a plugin.
 547   * @uses WP_PLUGIN_DIR
 548   */
 549  function plugin_basename($file) {
 550      $file = str_replace('\\','/',$file); // sanitize for Win32 installs
 551      $file = preg_replace('|/+|','/', $file); // remove any duplicate slash
 552      $plugin_dir = str_replace('\\','/',WP_PLUGIN_DIR); // sanitize for Win32 installs
 553      $plugin_dir = preg_replace('|/+|','/', $plugin_dir); // remove any duplicate slash
 554      $mu_plugin_dir = str_replace('\\','/',WPMU_PLUGIN_DIR); // sanitize for Win32 installs
 555      $mu_plugin_dir = preg_replace('|/+|','/', $mu_plugin_dir); // remove any duplicate slash
 556      $file = preg_replace('#^' . preg_quote($plugin_dir, '#') . '/|^' . preg_quote($mu_plugin_dir, '#') . '/#','',$file); // get relative path from plugins dir
 557      $file = trim($file, '/');
 558      return $file;
 559  }
 560  
 561  /**
 562   * Gets the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in
 563   * @package WordPress
 564   * @subpackage Plugin
 565   * @since 2.8
 566   *
 567   * @param string $file The filename of the plugin (__FILE__)
 568   * @return string the filesystem path of the directory that contains the plugin
 569   */
 570  function plugin_dir_path( $file ) {
 571      return trailingslashit( dirname( $file ) );
 572  }
 573  
 574  /**
 575   * Gets the URL directory path (with trailing slash) for the plugin __FILE__ passed in
 576   * @package WordPress
 577   * @subpackage Plugin
 578   * @since 2.8
 579   *
 580   * @param string $file The filename of the plugin (__FILE__)
 581   * @return string the URL path of the directory that contains the plugin
 582   */
 583  function plugin_dir_url( $file ) {
 584      return trailingslashit( plugins_url( '', $file ) );
 585  }
 586  
 587  /**
 588   * Set the activation hook for a plugin.
 589   *
 590   * When a plugin is activated, the action 'activate_PLUGINNAME' hook is
 591   * activated. In the name of this hook, PLUGINNAME is replaced with the name of
 592   * the plugin, including the optional subdirectory. For example, when the plugin
 593   * is located in wp-content/plugin/sampleplugin/sample.php, then the name of
 594   * this hook will become 'activate_sampleplugin/sample.php'. When the plugin
 595   * consists of only one file and is (as by default) located at
 596   * wp-content/plugin/sample.php the name of this hook will be
 597   * 'activate_sample.php'.
 598   *
 599   * @package WordPress
 600   * @subpackage Plugin
 601   * @since 2.0
 602   *
 603   * @param string $file The filename of the plugin including the path.
 604   * @param callback $function the function hooked to the 'activate_PLUGIN' action.
 605   */
 606  function register_activation_hook($file, $function) {
 607      $file = plugin_basename($file);
 608      add_action('activate_' . $file, $function);
 609  }
 610  
 611  /**
 612   * Set the deactivation hook for a plugin.
 613   *
 614   * When a plugin is deactivated, the action 'deactivate_PLUGINNAME' hook is
 615   * deactivated. In the name of this hook, PLUGINNAME is replaced with the name
 616   * of the plugin, including the optional subdirectory. For example, when the
 617   * plugin is located in wp-content/plugin/sampleplugin/sample.php, then
 618   * the name of this hook will become 'activate_sampleplugin/sample.php'.
 619   *
 620   * When the plugin consists of only one file and is (as by default) located at
 621   * wp-content/plugin/sample.php the name of this hook will be
 622   * 'activate_sample.php'.
 623   *
 624   * @package WordPress
 625   * @subpackage Plugin
 626   * @since 2.0
 627   *
 628   * @param string $file The filename of the plugin including the path.
 629   * @param callback $function the function hooked to the 'activate_PLUGIN' action.
 630   */
 631  function register_deactivation_hook($file, $function) {
 632      $file = plugin_basename($file);
 633      add_action('deactivate_' . $file, $function);
 634  }
 635  
 636  /**
 637   * Set the uninstallation hook for a plugin.
 638   *
 639   * Registers the uninstall hook that will be called when the user clicks on the
 640   * uninstall link that calls for the plugin to uninstall itself. The link won't
 641   * be active unless the plugin hooks into the action.
 642   *
 643   * The plugin should not run arbitrary code outside of functions, when
 644   * registering the uninstall hook. In order to run using the hook, the plugin
 645   * will have to be included, which means that any code laying outside of a
 646   * function will be run during the uninstall process. The plugin should not
 647   * hinder the uninstall process.
 648   *
 649   * If the plugin can not be written without running code within the plugin, then
 650   * the plugin should create a file named 'uninstall.php' in the base plugin
 651   * folder. This file will be called, if it exists, during the uninstall process
 652   * bypassing the uninstall hook. The plugin, when using the 'uninstall.php'
 653   * should always check for the 'WP_UNINSTALL_PLUGIN' constant, before
 654   * executing.
 655   *
 656   * @since 2.7
 657   *
 658   * @param string $file
 659   * @param callback $callback The callback to run when the hook is called.
 660   */
 661  function register_uninstall_hook($file, $callback) {
 662      // The option should not be autoloaded, because it is not needed in most
 663      // cases. Emphasis should be put on using the 'uninstall.php' way of
 664      // uninstalling the plugin.
 665      $uninstallable_plugins = (array) get_option('uninstall_plugins');
 666      $uninstallable_plugins[plugin_basename($file)] = $callback;
 667      update_option('uninstall_plugins', $uninstallable_plugins);
 668  }
 669  
 670  /**
 671   * Calls the 'all' hook, which will process the functions hooked into it.
 672   *
 673   * The 'all' hook passes all of the arguments or parameters that were used for
 674   * the hook, which this function was called for.
 675   *
 676   * This function is used internally for apply_filters(), do_action(), and
 677   * do_action_ref_array() and is not meant to be used from outside those
 678   * functions. This function does not check for the existence of the all hook, so
 679   * it will fail unless the all hook exists prior to this function call.
 680   *
 681   * @package WordPress
 682   * @subpackage Plugin
 683   * @since 2.5
 684   * @access private
 685   *
 686   * @uses $wp_filter Used to process all of the functions in the 'all' hook
 687   *
 688   * @param array $args The collected parameters from the hook that was called.
 689   * @param string $hook Optional. The hook name that was used to call the 'all' hook.
 690   */
 691  function _wp_call_all_hook($args) {
 692      global $wp_filter;
 693  
 694      reset( $wp_filter['all'] );
 695      do {
 696          foreach( (array) current($wp_filter['all']) as $the_ )
 697              if ( !is_null($the_['function']) )
 698                  call_user_func_array($the_['function'], $args);
 699  
 700      } while ( next($wp_filter['all']) !== false );
 701  }
 702  
 703  /**
 704   * Build Unique ID for storage and retrieval.
 705   *
 706   * The old way to serialize the callback caused issues and this function is the
 707   * solution. It works by checking for objects and creating an a new property in
 708   * the class to keep track of the object and new objects of the same class that
 709   * need to be added.
 710   *
 711   * It also allows for the removal of actions and filters for objects after they
 712   * change class properties. It is possible to include the property $wp_filter_id
 713   * in your class and set it to "null" or a number to bypass the workaround.
 714   * However this will prevent you from adding new classes and any new classes
 715   * will overwrite the previous hook by the same class.
 716   *
 717   * Functions and static method callbacks are just returned as strings and
 718   * shouldn't have any speed penalty.
 719   *
 720   * @package WordPress
 721   * @subpackage Plugin
 722   * @access private
 723   * @since 2.2.3
 724   * @link http://trac.wordpress.org/ticket/3875
 725   *
 726   * @global array $wp_filter Storage for all of the filters and actions
 727   * @param string $tag Used in counting how many hooks were applied
 728   * @param callback $function Used for creating unique id
 729   * @param int|bool $priority Used in counting how many hooks were applied.  If === false and $function is an object reference, we return the unique id only if it already has one, false otherwise.
 730   * @param string $type filter or action
 731   * @return string|bool Unique ID for usage as array key or false if $priority === false and $function is an object reference, and it does not already have a uniqe id.
 732   */
 733  function _wp_filter_build_unique_id($tag, $function, $priority) {
 734      global $wp_filter;
 735      static $filter_id_count = 0;
 736  
 737      if ( is_string($function) )
 738          return $function;
 739  
 740      $function = (array) $function;
 741  
 742      if (is_object($function[0]) ) {
 743          // Object Class Calling
 744          if ( function_exists('spl_object_hash') ) {
 745              return spl_object_hash($function[0]) . $function[1];
 746          } else {
 747              $obj_idx = get_class($function[0]).$function[1];
 748              if ( !isset($function[0]->wp_filter_id) ) {
 749                  if ( false === $priority )
 750                      return false;
 751                  $obj_idx .= isset($wp_filter[$tag][$priority]) ? count((array)$wp_filter[$tag][$priority]) : $filter_id_count;
 752                  $function[0]->wp_filter_id = $filter_id_count;
 753                  ++$filter_id_count;
 754              } else {
 755                  $obj_idx .= $function[0]->wp_filter_id;
 756              }
 757  
 758              return $obj_idx;
 759          }
 760      } else if ( is_string($function[0]) ) {
 761          // Static Calling
 762          return $function[0].$function[1];
 763      }
 764  }
 765  
 766  ?>