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  * Call hook functions defined in $wgHooks
  28  *
  29  * Because programmers assign to $wgHooks, we need to be very
  30  * careful about its contents. So, there's a lot more error-checking
  31  * in here than would normally be necessary.
  32  *
  33  * @param $event String: event name
  34  * @param $args Array: parameters passed to hook functions
  35  * @return Boolean
  36  */
  37 function wfRunHooks( $event, $args = array() ) {
  38         return Hooks::run( $event, $args );
  39 }
  40
  41 function hookErrorHandler( $errno, $errstr ) {
  42         return Hooks::hookErrorHandler( $errno, $errstr );
  43 }
  44
  45 class MWHookException extends MWException {}
  46
  47 /**
  48  * Hooks class.
  49  *
  50  * Used to supersede $wgHooks, because globals are EVIL.
  51  */
  52 class Hooks {
  53
  54         protected static $handlers = array();
  55
  56         /**
  57          * Attach an event handler to a given hook
  58          *
  59          * @param $name Mixed: name of hook
  60          * @param $callback Mixed: callback function to attach
  61          * @return void
  62          */
  63         public static function register( $name, $callback ) {
  64                 if( !isset( self::$handlers[$name] ) ) {
  65                         self::$handlers[$name] = array();
  66                 }
  67
  68                 self::$handlers[$name][] = $callback;
  69         }
  70
  71         /**
  72          * Returns true if a hook has a function registered to it.
  73          *
  74          * @param $name Mixed: name of hook
  75          * @return Boolean: true if a hook has a function registered to it
  76          */
  77         public static function isRegistered( $name ) {
  78                 if( !isset( self::$handlers[$name] ) ) {
  79                         self::$handlers[$name] = array();
  80                 }
  81
  82                 return ( count( self::$handlers[$name] ) != 0 );
  83         }
  84
  85         /**
  86          * Returns an array of all the event functions attached to a hook
  87          *
  88          * @param $name Mixed: name of the hook
  89          * @return array
  90          */
  91         public static function getHandlers( $name ) {
  92                 if( !isset( self::$handlers[$name] ) ) {
  93                         return array();
  94                 }
  95
  96                 return self::$handlers[$name];
  97         }
  98
  99         /**
 100          * Call hook functions defined in Hooks::register
 101          *
 102          * Because programmers assign to $wgHooks, we need to be very
 103          * careful about its contents. So, there's a lot more error-checking
 104          * in here than would normally be necessary.
 105          *
 106          * @param $event String: event name
 107          * @param $args Array: parameters passed to hook functions
 108          * @return Boolean
 109          */
 110         public static function run( $event, $args = array() ) {
 111                 global $wgHooks;
 112
 113                 // Return quickly in the most common case
 114                 if ( !isset( self::$handlers[$event] ) && !isset( $wgHooks[$event] ) ) {
 115                         return true;
 116                 }
 117
 118                 if ( !is_array( self::$handlers ) ) {
 119                         throw new MWException( "Local hooks array is not an array!\n" );
 120                 }
 121
 122                 if ( !is_array( $wgHooks ) ) {
 123                         throw new MWException( "Global hooks array is not an array!\n" );
 124                 }
 125
 126                 $new_handlers = (array) self::$handlers;
 127                 $old_handlers = (array) $wgHooks;
 128
 129                 $hook_array = array_merge( $new_handlers, $old_handlers );
 130
 131                 if ( !is_array( $hook_array[$event] ) ) {
 132                         throw new MWException( "Hooks array for event '$event' is not an array!\n" );
 133                 }
 134
 135                 foreach ( $hook_array[$event] as $index => $hook ) {
 136                         $object = null;
 137                         $method = null;
 138                         $func = null;
 139                         $data = null;
 140                         $have_data = false;
 141                         $closure = false;
 142                         $badhookmsg = false;
 143
 144                         /**
 145                          * $hook can be: a function, an object, an array of $function and
 146                          * $data, an array of just a function, an array of object and
 147                          * method, or an array of object, method, and data.
 148                          */
 149                         if ( is_array( $hook ) ) {
 150                                 if ( count( $hook ) < 1 ) {
 151                                         throw new MWException( 'Empty array in hooks for ' . $event . "\n" );
 152                                 } elseif ( is_object( $hook[0] ) ) {
 153                                         $object = $hook_array[$event][$index][0];
 154                                         if ( $object instanceof Closure ) {
 155                                                 $closure = true;
 156                                                 if ( count( $hook ) > 1 ) {
 157                                                         $data = $hook[1];
 158                                                         $have_data = true;
 159                                                 }
 160                                         } else {
 161                                                 if ( count( $hook ) < 2 ) {
 162                                                         $method = 'on' . $event;
 163                                                 } else {
 164                                                         $method = $hook[1];
 165                                                         if ( count( $hook ) > 2 ) {
 166                                                                 $data = $hook[2];
 167                                                                 $have_data = true;
 168                                                         }
 169                                                 }
 170                                         }
 171                                 } elseif ( is_string( $hook[0] ) ) {
 172                                         $func = $hook[0];
 173                                         if ( count( $hook ) > 1) {
 174                                                 $data = $hook[1];
 175                                                 $have_data = true;
 176                                         }
 177                                 } else {
 178                                         throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 179                                 }
 180                         } elseif ( is_string( $hook ) ) { # functions look like strings, too
 181                                 $func = $hook;
 182                         } elseif ( is_object( $hook ) ) {
 183                                 $object = $hook_array[$event][$index];
 184                                 if ( $object instanceof Closure ) {
 185                                         $closure = true;
 186                                 } else {
 187                                         $method = "on" . $event;
 188                                 }
 189                         } else {
 190                                 throw new MWException( 'Unknown datatype in hooks for ' . $event . "\n" );
 191                         }
 192
 193                         /* We put the first data element on, if needed. */
 194                         if ( $have_data ) {
 195                                 $hook_args = array_merge( array( $data ), $args );
 196                         } else {
 197                                 $hook_args = $args;
 198                         }
 199
 200                         if ( $closure ) {
 201                                 $callback = $object;
 202                                 $func = "hook-$event-closure";
 203                         } elseif ( isset( $object ) ) {
 204                                 $func = get_class( $object ) . '::' . $method;
 205                                 $callback = array( $object, $method );
 206                         } else {
 207                                 $callback = $func;
 208                         }
 209
 210                         // Run autoloader (workaround for call_user_func_array bug)
 211                         is_callable( $callback );
 212
 213                         /**
 214                          * Call the hook. The documentation of call_user_func_array clearly
 215                          * states that FALSE is returned on failure. However this is not
 216                          * case always. In some version of PHP if the function signature
 217                          * does not match the call signature, PHP will issue an warning:
 218                          * Param y in x expected to be a reference, value given.
 219                          *
 220                          * In that case the call will also return null. The following code
 221                          * catches that warning and provides better error message. The
 222                          * function documentation also says that:
 223                          *     In other words, it does not depend on the function signature
 224                          *     whether the parameter is passed by a value or by a reference.
 225                          * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
 226                          * is unsurprisingly marked as bogus. In short handling of failures
 227                          * with call_user_func_array is a failure, the documentation for that
 228                          * function is wrong and misleading and PHP developers don't see any
 229                          * problem here.
 230                          */
 231                         $retval = null;
 232                         set_error_handler( array( 'Hooks', 'hookErrorHandler' ) );
 233                         wfProfileIn( $func );
 234                         try {
 235                                 $retval = call_user_func_array( $callback, $hook_args );
 236                         } catch ( MWHookException $e ) {
 237                                 $badhookmsg = $e->getMessage();
 238                         }
 239                         wfProfileOut( $func );
 240                         restore_error_handler();
 241
 242                         /* String return is an error; false return means stop processing. */
 243                         if ( is_string( $retval ) ) {
 244                                 global $wgOut;
 245                                 $wgOut->showFatalError( $retval );
 246                                 return false;
 247                         } elseif( $retval === null ) {
 248                                 if ( $closure ) {
 249                                         $prettyFunc = "$event closure";
 250                                 } elseif( is_array( $callback ) ) {
 251                                         if( is_object( $callback[0] ) ) {
 252                                                 $prettyClass = get_class( $callback[0] );
 253                                         } else {
 254                                                 $prettyClass = strval( $callback[0] );
 255                                         }
 256                                         $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
 257                                 } else {
 258                                         $prettyFunc = strval( $callback );
 259                                 }
 260                                 if ( $badhookmsg ) {
 261                                         throw new MWException(
 262                                                 'Detected bug in an extension! ' .
 263                                                 "Hook $prettyFunc has invalid call signature; " . $badhookmsg
 264                                         );
 265                                 } else {
 266                                         throw new MWException(
 267                                                 'Detected bug in an extension! ' .
 268                                                 "Hook $prettyFunc failed to return a value; " .
 269                                                 'should return true to continue hook processing or false to abort.'
 270                                         );
 271                                 }
 272                         } else if ( !$retval ) {
 273                                 return false;
 274                         }
 275                 }
 276
 277                 return true;
 278         }
 279
 280         /**
 281          * This REALLY should be protected... but it's public for compatibility
 282          *
 283          * @param $errno Unused
 284          * @param $errstr String: error message
 285          * @return Boolean: false
 286          */
 287         public static function hookErrorHandler( $errno, $errstr ) {
 288                 if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
 289                         throw new MWHookException( $errstr );
 290                 }
 291                 return false;
 292         }
 293 }