includes/Hooks.php

   1 <?php
   2 /**
   3  * A tool for running hook functions.
   4  *
   5  * Copyright 2004, 2005 Evan Prodromou <evan@wikitravel.org>.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
  20  *
  21  * @author Evan Prodromou <evan@wikitravel.org>
  22  * @see hooks.txt
  23  * @file
  24  */
  25
  26 class MWHookException extends MWException {}
  27
  28 /**
  29  * Hooks class.
  30  *
  31  * Used to supersede $wgHooks, because globals are EVIL.
  32  */
  33 class Hooks {
  34
  35         protected static $handlers = array();
  36
  37         /**
  38          * Attach an event handler to a given hook
  39          *
  40          * @param $name Mixed: name of hook
  41          * @param $callback Mixed: callback function to attach
  42          */
  43         public static function register( $name, $callback ) {
  44                 if( !isset( self::$handlers[$name] ) ) {
  45                         self::$handlers[$name] = array();
  46                 }
  47
  48                 self::$handlers[$name][] = $callback;
  49         }
  50
  51         /**
  52          * Returns true if a hook has a function registered to it.
  53          *
  54          * @param $name Mixed: name of hook
  55          * @return Boolean: true if a hook has a function registered to it
  56          */
  57         public static function isRegistered( $name ) {
  58                 if( !isset( self::$handlers[$name] ) ) {
  59                         self::$handlers[$name] = array();
  60                 }
  61
  62                 return ( count( self::$handlers[$name] ) != 0 );
  63         }
  64
  65         /**
  66          * Returns an array of all the event functions attached to a hook
  67          *
  68          * @param $name Mixed: name of the hook
  69          * @return array
  70          */
  71         public static function getHandlers( $name ) {
  72                 if( !isset( self::$handlers[$name] ) ) {
  73                         return array();
  74                 }
  75
  76                 return self::$handlers[$name];
  77         }
  78
  79         /**
  80          * Call hook functions defined in Hooks::register
  81          *
  82          * Because programmers assign to $wgHooks, we need to be very
  83          * careful about its contents. So, there's a lot more error-checking
  84          * in here than would normally be necessary.
  85          *
  86          * @param $event String: event name
  87          * @param $args Array: parameters passed to hook functions
  88          * @return Boolean True if no handler aborted the hook
  89          */
  90         public static function run( $event, $args = array() ) {
  91                 global $wgHooks;
  92
  93                 // Return quickly in the most common case
  94                 if ( !isset( self::$handlers[$event] ) && !isset( $wgHooks[$event] ) ) {
  95                         return true;
  96                 }
  97
  98                 if ( !is_array( self::$handlers ) ) {
  99                         throw new MWException( "Local hooks array is not an array!\n" );
 100                 }
 101
 102                 if ( !is_array( $wgHooks ) ) {
 103                         throw new MWException( "Global hooks array is not an array!\n" );
 104                 }
 105
 106                 $new_handlers = (array) self::$handlers;
 107                 $old_handlers = (array) $wgHooks;
 108
 109                 $hook_array = array_merge( $new_handlers, $old_handlers );
 110
 111                 if ( !is_array( $hook_array[$event] ) ) {
 112                         throw new MWException( "Hooks array for event '$event' is not an array!\n" );
 113                 }
 114
 115                 foreach ( $hook_array[$event] as $index => $hook ) {
 116                         $object = null;
 117                         $method = null;
 118                         $func = null;
 119                         $data = null;
 120                         $have_data = false;
 121                         $closure = false;
 122                         $badhookmsg = false;
 123
 124                         /**
 125                          * $hook can be: a function, an object, an array of $function and
 126                          * $data, an array of just a function, an array of object and
 127                          * method, or an array of object, method, and data.
 128                          */
 129                         if ( is_array( $hook ) ) {
 130                                 if ( count( $hook ) < 1 ) {
 131                                         throw new MWException( 'Empty array in hooks for ' . $event . "\n" );
 132                                 } elseif ( is_object( $hook[0] ) ) {
 133                                         $object = $hook_array[$event][$index][0];
 134                                         if ( $object instanceof Closure ) {
 135                                                 $closure = true;
 136                                                 if ( count( $hook ) > 1 ) {
 137                                                         $data = $hook[1];
 138                                                         $have_data = true;
 139                                                 }
 140                                         } else {
 141                                                 if ( count( $hook ) < 2 ) {
 142                                                         $method = 'on' . $event;
 143                                                 } else {
 144                                                         $method = $hook[1];
 145                                                         if ( count( $hook ) > 2 ) {
 146                                                                 $data = $hook[2];
 147                                                                 $have_data = true;
 148                                                         }
 149                                                 }
 150                                         }
 151                                 } elseif ( is_string( $hook[0] ) ) {
 152                                         $func = $hook[0];
 153                                         if ( count( $hook ) > 1) {
 154                                                 $data = $hook[1];
 155                                                 $have_data = true;
 156                                         }
 157                                 } else {
 158                                         throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 159                                 }
 160                         } elseif ( is_string( $hook ) ) { # functions look like strings, too
 161                                 $func = $hook;
 162                         } elseif ( is_object( $hook ) ) {
 163                                 $object = $hook_array[$event][$index];
 164                                 if ( $object instanceof Closure ) {
 165                                         $closure = true;
 166                                 } else {
 167                                         $method = "on" . $event;
 168                                 }
 169                         } else {
 170                                 throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 171                         }
 172
 173                         /* We put the first data element on, if needed. */
 174                         if ( $have_data ) {
 175                                 $hook_args = array_merge( array( $data ), $args );
 176                         } else {
 177                                 $hook_args = $args;
 178                         }
 179
 180                         if ( $closure ) {
 181                                 $callback = $object;
 182                                 $func = "hook-$event-closure";
 183                         } elseif ( isset( $object ) ) {
 184                                 $func = get_class( $object ) . '::' . $method;
 185                                 $callback = array( $object, $method );
 186                         } else {
 187                                 $callback = $func;
 188                         }
 189
 190                         // Run autoloader (workaround for call_user_func_array bug)
 191                         is_callable( $callback );
 192
 193                         /**
 194                          * Call the hook. The documentation of call_user_func_array clearly
 195                          * states that FALSE is returned on failure. However this is not
 196                          * case always. In some version of PHP if the function signature
 197                          * does not match the call signature, PHP will issue an warning:
 198                          * Param y in x expected to be a reference, value given.
 199                          *
 200                          * In that case the call will also return null. The following code
 201                          * catches that warning and provides better error message. The
 202                          * function documentation also says that:
 203                          *     In other words, it does not depend on the function signature
 204                          *     whether the parameter is passed by a value or by a reference.
 205                          * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
 206                          * is unsurprisingly marked as bogus. In short handling of failures
 207                          * with call_user_func_array is a failure, the documentation for that
 208                          * function is wrong and misleading and PHP developers don't see any
 209                          * problem here.
 210                          */
 211                         $retval = null;
 212                         set_error_handler( 'Hooks::hookErrorHandler' );
 213                         wfProfileIn( $func );
 214                         try {
 215                                 $retval = call_user_func_array( $callback, $hook_args );
 216                         } catch ( MWHookException $e ) {
 217                                 $badhookmsg = $e->getMessage();
 218                         }
 219                         wfProfileOut( $func );
 220                         restore_error_handler();
 221
 222                         /* String return is an error; false return means stop processing. */
 223                         if ( is_string( $retval ) ) {
 224                                 throw new FatalError( $retval );
 225                         } elseif( $retval === null ) {
 226                                 if ( $closure ) {
 227                                         $prettyFunc = "$event closure";
 228                                 } elseif( is_array( $callback ) ) {
 229                                         if( is_object( $callback[0] ) ) {
 230                                                 $prettyClass = get_class( $callback[0] );
 231                                         } else {
 232                                                 $prettyClass = strval( $callback[0] );
 233                                         }
 234                                         $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
 235                                 } else {
 236                                         $prettyFunc = strval( $callback );
 237                                 }
 238                                 if ( $badhookmsg ) {
 239                                         throw new MWException(
 240                                                 'Detected bug in an extension! ' .
 241                                                 "Hook $prettyFunc has invalid call signature; " . $badhookmsg
 242                                         );
 243                                 } else {
 244                                         throw new MWException(
 245                                                 'Detected bug in an extension! ' .
 246                                                 "Hook $prettyFunc failed to return a value; " .
 247                                                 'should return true to continue hook processing or false to abort.'
 248                                         );
 249                                 }
 250                         } elseif ( !$retval ) {
 251                                 return false;
 252                         }
 253                 }
 254
 255                 return true;
 256         }
 257
 258         /**
 259          * This REALLY should be protected... but it's public for compatibility
 260          *
 261          * @param $errno Unused
 262          * @param $errstr String: error message
 263          * @return Boolean: false
 264          */
 265         public static function hookErrorHandler( $errno, $errstr ) {
 266                 if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
 267                         throw new MWHookException( $errstr );
 268                 }
 269                 return false;
 270         }
 271 }