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 /**
  27  * @since 1.18
  28  */
  29 class MWHookException extends MWException {}
  30
  31 /**
  32  * Hooks class.
  33  *
  34  * Used to supersede $wgHooks, because globals are EVIL.
  35  *
  36  * @since 1.18
  37  */
  38 class Hooks {
  39
  40         protected static $handlers = array();
  41
  42         /**
  43          * Attach an event handler to a given hook
  44          *
  45          * @since 1.18
  46          *
  47          * @param $name Mixed: name of hook
  48          * @param $callback Mixed: callback function to attach
  49          */
  50         public static function register( $name, $callback ) {
  51                 if( !isset( self::$handlers[$name] ) ) {
  52                         self::$handlers[$name] = array();
  53                 }
  54
  55                 self::$handlers[$name][] = $callback;
  56         }
  57
  58         /**
  59          * Returns true if a hook has a function registered to it.
  60          *
  61          * @since 1.18
  62          *
  63          * @param $name Mixed: name of hook
  64          * @return Boolean: true if a hook has a function registered to it
  65          */
  66         public static function isRegistered( $name ) {
  67                 if( !isset( self::$handlers[$name] ) ) {
  68                         self::$handlers[$name] = array();
  69                 }
  70
  71                 return ( count( self::$handlers[$name] ) != 0 );
  72         }
  73
  74         /**
  75          * Returns an array of all the event functions attached to a hook
  76          *
  77          * @since 1.18
  78          *
  79          * @param $name Mixed: name of the hook
  80          * @return array
  81          */
  82         public static function getHandlers( $name ) {
  83                 if( !isset( self::$handlers[$name] ) ) {
  84                         return array();
  85                 }
  86
  87                 return self::$handlers[$name];
  88         }
  89
  90         /**
  91          * Call hook functions defined in Hooks::register
  92          *
  93          * Because programmers assign to $wgHooks, we need to be very
  94          * careful about its contents. So, there's a lot more error-checking
  95          * in here than would normally be necessary.
  96          *
  97          * @since 1.18
  98          *
  99          * @param $event String: event name
 100          * @param $args Array: parameters passed to hook functions
 101          * @throws MWException
 102          * @throws FatalError
 103          * @return Boolean True if no handler aborted the hook
 104          */
 105         public static function run( $event, $args = array() ) {
 106                 global $wgHooks;
 107
 108                 // Return quickly in the most common case
 109                 if ( !isset( self::$handlers[$event] ) && !isset( $wgHooks[$event] ) ) {
 110                         return true;
 111                 }
 112
 113                 if ( !is_array( self::$handlers ) ) {
 114                         throw new MWException( "Local hooks array is not an array!\n" );
 115                 }
 116
 117                 if ( !is_array( $wgHooks ) ) {
 118                         throw new MWException( "Global hooks array is not an array!\n" );
 119                 }
 120
 121                 $new_handlers = (array) self::$handlers;
 122                 $old_handlers = (array) $wgHooks;
 123
 124                 $hook_array = array_merge( $new_handlers, $old_handlers );
 125
 126                 if ( !is_array( $hook_array[$event] ) ) {
 127                         throw new MWException( "Hooks array for event '$event' is not an array!\n" );
 128                 }
 129
 130                 foreach ( $hook_array[$event] as $index => $hook ) {
 131                         $object = null;
 132                         $method = null;
 133                         $func = null;
 134                         $data = null;
 135                         $have_data = false;
 136                         $closure = false;
 137                         $badhookmsg = false;
 138
 139                         /**
 140                          * $hook can be: a function, an object, an array of $function and
 141                          * $data, an array of just a function, an array of object and
 142                          * method, or an array of object, method, and data.
 143                          */
 144                         if ( is_array( $hook ) ) {
 145                                 if ( count( $hook ) < 1 ) {
 146                                         throw new MWException( 'Empty array in hooks for ' . $event . "\n" );
 147                                 } elseif ( is_object( $hook[0] ) ) {
 148                                         $object = $hook_array[$event][$index][0];
 149                                         if ( $object instanceof Closure ) {
 150                                                 $closure = true;
 151                                                 if ( count( $hook ) > 1 ) {
 152                                                         $data = $hook[1];
 153                                                         $have_data = true;
 154                                                 }
 155                                         } else {
 156                                                 if ( count( $hook ) < 2 ) {
 157                                                         $method = 'on' . $event;
 158                                                 } else {
 159                                                         $method = $hook[1];
 160                                                         if ( count( $hook ) > 2 ) {
 161                                                                 $data = $hook[2];
 162                                                                 $have_data = true;
 163                                                         }
 164                                                 }
 165                                         }
 166                                 } elseif ( is_string( $hook[0] ) ) {
 167                                         $func = $hook[0];
 168                                         if ( count( $hook ) > 1) {
 169                                                 $data = $hook[1];
 170                                                 $have_data = true;
 171                                         }
 172                                 } else {
 173                                         throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 174                                 }
 175                         } elseif ( is_string( $hook ) ) { # functions look like strings, too
 176                                 $func = $hook;
 177                         } elseif ( is_object( $hook ) ) {
 178                                 $object = $hook_array[$event][$index];
 179                                 if ( $object instanceof Closure ) {
 180                                         $closure = true;
 181                                 } else {
 182                                         $method = "on" . $event;
 183                                 }
 184                         } else {
 185                                 throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 186                         }
 187
 188                         /* We put the first data element on, if needed. */
 189                         if ( $have_data ) {
 190                                 $hook_args = array_merge( array( $data ), $args );
 191                         } else {
 192                                 $hook_args = $args;
 193                         }
 194
 195                         if ( $closure ) {
 196                                 $callback = $object;
 197                                 $func = "hook-$event-closure";
 198                         } elseif ( isset( $object ) ) {
 199                                 $func = get_class( $object ) . '::' . $method;
 200                                 $callback = array( $object, $method );
 201                         } else {
 202                                 $callback = $func;
 203                         }
 204
 205                         // Run autoloader (workaround for call_user_func_array bug)
 206                         is_callable( $callback );
 207
 208                         /**
 209                          * Call the hook. The documentation of call_user_func_array clearly
 210                          * states that FALSE is returned on failure. However this is not
 211                          * case always. In some version of PHP if the function signature
 212                          * does not match the call signature, PHP will issue an warning:
 213                          * Param y in x expected to be a reference, value given.
 214                          *
 215                          * In that case the call will also return null. The following code
 216                          * catches that warning and provides better error message. The
 217                          * function documentation also says that:
 218                          *     In other words, it does not depend on the function signature
 219                          *     whether the parameter is passed by a value or by a reference.
 220                          * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
 221                          * is unsurprisingly marked as bogus. In short handling of failures
 222                          * with call_user_func_array is a failure, the documentation for that
 223                          * function is wrong and misleading and PHP developers don't see any
 224                          * problem here.
 225                          */
 226                         $retval = null;
 227                         set_error_handler( 'Hooks::hookErrorHandler' );
 228                         wfProfileIn( $func );
 229                         try {
 230                                 $retval = call_user_func_array( $callback, $hook_args );
 231                         } catch ( MWHookException $e ) {
 232                                 $badhookmsg = $e->getMessage();
 233                         }
 234                         wfProfileOut( $func );
 235                         restore_error_handler();
 236
 237                         /* String return is an error; false return means stop processing. */
 238                         if ( is_string( $retval ) ) {
 239                                 throw new FatalError( $retval );
 240                         } elseif( $retval === null ) {
 241                                 if ( $closure ) {
 242                                         $prettyFunc = "$event closure";
 243                                 } elseif( is_array( $callback ) ) {
 244                                         if( is_object( $callback[0] ) ) {
 245                                                 $prettyClass = get_class( $callback[0] );
 246                                         } else {
 247                                                 $prettyClass = strval( $callback[0] );
 248                                         }
 249                                         $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
 250                                 } else {
 251                                         $prettyFunc = strval( $callback );
 252                                 }
 253                                 if ( $badhookmsg ) {
 254                                         throw new MWException(
 255                                                 'Detected bug in an extension! ' .
 256                                                 "Hook $prettyFunc has invalid call signature; " . $badhookmsg
 257                                         );
 258                                 } else {
 259                                         throw new MWException(
 260                                                 'Detected bug in an extension! ' .
 261                                                 "Hook $prettyFunc failed to return a value; " .
 262                                                 'should return true to continue hook processing or false to abort.'
 263                                         );
 264                                 }
 265                         } elseif ( !$retval ) {
 266                                 return false;
 267                         }
 268                 }
 269
 270                 return true;
 271         }
 272
 273         /**
 274          * This REALLY should be protected... but it's public for compatibility
 275          *
 276          * @since 1.18
 277          *
 278          * @param $errno int Unused
 279          * @param $errstr String: error message
 280          * @throws MWHookException
 281          * @return Boolean: false
 282          */
 283         public static function hookErrorHandler( $errno, $errstr ) {
 284                 if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
 285                         throw new MWHookException( $errstr );
 286                 }
 287                 return false;
 288         }
 289 }