includes/Hooks.php

   1 <?php
   2
   3 /**
   4  * A tool for running hook functions.
   5  *
   6  * Copyright 2004, 2005 Evan Prodromou <evan@wikitravel.org>.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
  21  *
  22  * @author Evan Prodromou <evan@wikitravel.org>
  23  * @see hooks.txt
  24  * @file
  25  */
  26
  27 /**
  28  * Hooks class.
  29  *
  30  * Used to supersede $wgHooks, because globals are EVIL.
  31  *
  32  * @since 1.18
  33  */
  34 class Hooks {
  35         /**
  36          * Array of events mapped to an array of callbacks to be run
  37          * when that event is triggered.
  38          */
  39         protected static $handlers = array();
  40
  41         /**
  42          * Attach an event handler to a given hook.
  43          *
  44          * @param string $name Name of hook
  45          * @param callable $callback Callback function to attach
  46          *
  47          * @since 1.18
  48          */
  49         public static function register( $name, $callback ) {
  50                 if ( !isset( self::$handlers[$name] ) ) {
  51                         self::$handlers[$name] = array();
  52                 }
  53
  54                 self::$handlers[$name][] = $callback;
  55         }
  56
  57         /**
  58          * Clears hooks registered via Hooks::register(). Does not touch $wgHooks.
  59          * This is intended for use while testing and will fail if MW_PHPUNIT_TEST is not defined.
  60          *
  61          * @param string $name The name of the hook to clear.
  62          *
  63          * @since 1.21
  64          * @throws MWException If not in testing mode.
  65          */
  66         public static function clear( $name ) {
  67                 if ( !defined( 'MW_PHPUNIT_TEST' ) ) {
  68                         throw new MWException( 'Cannot reset hooks in operation.' );
  69                 }
  70
  71                 unset( self::$handlers[$name] );
  72         }
  73
  74         /**
  75          * Returns true if a hook has a function registered to it.
  76          * The function may have been registered either via Hooks::register or in $wgHooks.
  77          *
  78          * @since 1.18
  79          *
  80          * @param string $name Name of hook
  81          * @return bool True if the hook has a function registered to it
  82          */
  83         public static function isRegistered( $name ) {
  84                 global $wgHooks;
  85                 return !empty( $wgHooks[$name] ) || !empty( self::$handlers[$name] );
  86         }
  87
  88         /**
  89          * Returns an array of all the event functions attached to a hook
  90          * This combines functions registered via Hooks::register and with $wgHooks.
  91          *
  92          * @since 1.18
  93          *
  94          * @param string $name Name of the hook
  95          * @return array
  96          */
  97         public static function getHandlers( $name ) {
  98                 global $wgHooks;
  99
 100                 if ( !self::isRegistered( $name ) ) {
 101                         return array();
 102                 } elseif ( !isset( self::$handlers[$name] ) ) {
 103                         return $wgHooks[$name];
 104                 } elseif ( !isset( $wgHooks[$name] ) ) {
 105                         return self::$handlers[$name];
 106                 } else {
 107                         return array_merge( self::$handlers[$name], $wgHooks[$name] );
 108                 }
 109         }
 110
 111         /**
 112          * Call hook functions defined in Hooks::register and $wgHooks.
 113          *
 114          * For a certain hook event, fetch the array of hook events and
 115          * process them. Determine the proper callback for each hook and
 116          * then call the actual hook using the appropriate arguments.
 117          * Finally, process the return value and return/throw accordingly.
 118          *
 119          * @param string $event Event name
 120          * @param array $args Array of parameters passed to hook functions
 121          * @param string|null $deprecatedVersion Optionally, mark hook as deprecated with version number
 122          * @return bool True if no handler aborted the hook
 123          *
 124          * @throws Exception
 125          * @throws FatalError
 126          * @throws MWException
 127          * @since 1.22 A hook function is not required to return a value for
 128          *   processing to continue. Not returning a value (or explicitly
 129          *   returning null) is equivalent to returning true.
 130          */
 131         public static function run( $event, array $args = array(), $deprecatedVersion = null ) {
 132                 foreach ( self::getHandlers( $event ) as $hook ) {
 133                         // Turn non-array values into an array. (Can't use casting because of objects.)
 134                         if ( !is_array( $hook ) ) {
 135                                 $hook = array( $hook );
 136                         }
 137
 138                         if ( !array_filter( $hook ) ) {
 139                                 // Either array is empty or it's an array filled with null/false/empty.
 140                                 continue;
 141                         } elseif ( is_array( $hook[0] ) ) {
 142                                 // First element is an array, meaning the developer intended
 143                                 // the first element to be a callback. Merge it in so that
 144                                 // processing can be uniform.
 145                                 $hook = array_merge( $hook[0], array_slice( $hook, 1 ) );
 146                         }
 147
 148                         /**
 149                          * $hook can be: a function, an object, an array of $function and
 150                          * $data, an array of just a function, an array of object and
 151                          * method, or an array of object, method, and data.
 152                          */
 153                         if ( $hook[0] instanceof Closure ) {
 154                                 $func = "hook-$event-closure";
 155                                 $callback = array_shift( $hook );
 156                         } elseif ( is_object( $hook[0] ) ) {
 157                                 $object = array_shift( $hook );
 158                                 $method = array_shift( $hook );
 159
 160                                 // If no method was specified, default to on$event.
 161                                 if ( $method === null ) {
 162                                         $method = "on$event";
 163                                 }
 164
 165                                 $func = get_class( $object ) . '::' . $method;
 166                                 $callback = array( $object, $method );
 167                         } elseif ( is_string( $hook[0] ) ) {
 168                                 $func = $callback = array_shift( $hook );
 169                         } else {
 170                                 throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 171                         }
 172
 173                         // Run autoloader (workaround for call_user_func_array bug)
 174                         // and throw error if not callable.
 175                         if ( !is_callable( $callback ) ) {
 176                                 throw new MWException( 'Invalid callback ' . $func . ' in hooks for ' . $event . "\n" );
 177                         }
 178
 179                         /*
 180                          * Call the hook. The documentation of call_user_func_array says
 181                          * false is returned on failure. However, if the function signature
 182                          * does not match the call signature, PHP will issue an warning and
 183                          * return null instead. The following code catches that warning and
 184                          * provides better error message.
 185                          */
 186                         $retval = null;
 187                         $badhookmsg = null;
 188                         $hook_args = array_merge( $hook, $args );
 189
 190                         // mark hook as deprecated, if deprecation version is specified
 191                         if ( $deprecatedVersion !== null ) {
 192                                 wfDeprecated( "$event hook (used in $func)", $deprecatedVersion );
 193                         }
 194
 195                         $retval = call_user_func_array( $callback, $hook_args );
 196
 197                         // Process the return value.
 198                         if ( is_string( $retval ) ) {
 199                                 // String returned means error.
 200                                 throw new FatalError( $retval );
 201                         } elseif ( $retval === false ) {
 202                                 // False was returned. Stop processing, but no error.
 203                                 return false;
 204                         }
 205                 }
 206
 207                 return true;
 208         }
 209 }