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