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 /**
  28  * Call hook functions defined in $wgHooks
  29  *
  30  * Because programmers assign to $wgHooks, we need to be very
  31  * careful about its contents. So, there's a lot more error-checking
  32  * in here than would normally be necessary.
  33  *
  34  * @param $event String: event name
  35  * @param $args Array: parameters passed to hook functions
  36  * @return Boolean
  37  */
  38 function wfRunHooks( $event, $args = array() ) {
  39         return Hooks::run( $event, $args );
  40 }
  41
  42 function hookErrorHandler( $errno, $errstr ) {
  43         return Hooks::hookErrorHandler( $errno, $errstr );
  44 }
  45
  46 class MWHookException extends MWException {}
  47
  48
  49 /**
  50  * Hooks class.
  51  *
  52  * Used to supersede $wgHooks, because globals are EVIL.
  53  *
  54  */
  55 class Hooks {
  56
  57         protected static $handlers = array();
  58
  59         /**
  60          * Attach an event handler to a given hook
  61          *
  62          * @access public
  63          * @param mixed $name Name of hook
  64          * @param mixed $callback Callback function to attach
  65          * @return void
  66          */
  67         public static function register( $name, $callback ) {
  68
  69                 if( !isset( self::$handlers[$name] ) ) {
  70                         self::$handlers[$name] = array();
  71                 }
  72
  73                 self::$handlers[$name][] = $callback;
  74
  75         }
  76
  77         /**
  78          * Returns true if a hook has a function registered to it.
  79          *
  80          * @access public
  81          * @param mixed $name Name of hook
  82          * @return bool
  83          */
  84         public static function isRegistered( $name ) {
  85
  86                 if( !isset( self::$handlers[$name] ) ) {
  87                         self::$handlers[$name] = array();
  88                 }
  89
  90                 return ( count( self::$handlers[$name] ) != 0 );
  91
  92         }
  93
  94         /**
  95          * Returns an array of all the event functions attached to a hook
  96          *
  97          * @access public
  98          * @param mixed $name Name of hook
  99          * @return array
 100          */
 101         public static function getHandlers( $name ) {
 102
 103                 if( !isset( self::$handlers[$name] ) ) {
 104                         return array();
 105                 }
 106
 107                 return self::$handlers[$name];
 108
 109         }
 110
 111
 112
 113
 114         /**
 115          * Call hook functions defined in Hooks::register
 116          *
 117          * Because programmers assign to $wgHooks, we need to be very
 118          * careful about its contents. So, there's a lot more error-checking
 119          * in here than would normally be necessary.
 120          *
 121          * @param $event String: event name
 122          * @param $args Array: parameters passed to hook functions
 123          * @return Boolean
 124          */
 125         public static function run( $event, $args = array() ) {
 126
 127                 global $wgHooks;
 128
 129                 // Return quickly in the most common case
 130                 if ( !isset( self::$handlers[$event] ) && !isset( $wgHooks[$event] ) ) {
 131                         return true;
 132                 }
 133
 134                 if (!is_array(self::$handlers)) {
 135                         throw new MWException("Local hooks array is not an array!\n");
 136                 }
 137
 138                 if (!is_array($wgHooks)) {
 139                         throw new MWException("Global hooks array is not an array!\n");
 140                 }
 141
 142                 $new_handlers = (array) self::$handlers;
 143                 $old_handlers = (array) $wgHooks;
 144
 145                 $hook_array = array_merge( $new_handlers, $old_handlers );
 146
 147                 if ( !is_array($hook_array[$event]) ) {
 148                         throw new MWException("Hooks array for event '$event' is not an array!\n");
 149                 }
 150
 151                 foreach ($hook_array[$event] as $index => $hook) {
 152
 153                         $object = null;
 154                         $method = null;
 155                         $func = null;
 156                         $data = null;
 157                         $have_data = false;
 158                         $closure = false;
 159                         $badhookmsg = false;
 160
 161                         /* $hook can be: a function, an object, an array of $function and $data,
 162                          * an array of just a function, an array of object and method, or an
 163                          * array of object, method, and data.
 164                          */
 165
 166                         if ( is_array( $hook ) ) {
 167                                 if ( count( $hook ) < 1 ) {
 168                                         throw new MWException("Empty array in hooks for " . $event . "\n");
 169                                 } else if ( is_object( $hook[0] ) ) {
 170                                         $object = $hook_array[$event][$index][0];
 171                                         if ( $object instanceof Closure ) {
 172                                                 $closure = true;
 173                                                 if ( count( $hook ) > 1 ) {
 174                                                         $data = $hook[1];
 175                                                         $have_data = true;
 176                                                 }
 177                                         } else {
 178                                                 if ( count( $hook ) < 2 ) {
 179                                                         $method = "on" . $event;
 180                                                 } else {
 181                                                         $method = $hook[1];
 182                                                         if ( count( $hook ) > 2 ) {
 183                                                                 $data = $hook[2];
 184                                                                 $have_data = true;
 185                                                         }
 186                                                 }
 187                                         }
 188                                 } else if ( is_string( $hook[0] ) ) {
 189                                         $func = $hook[0];
 190                                         if ( count( $hook ) > 1) {
 191                                                 $data = $hook[1];
 192                                                 $have_data = true;
 193                                         }
 194                                 } else {
 195                                         throw new MWException( "Unknown datatype in hooks for " . $event . "\n" );
 196                                 }
 197                         } else if ( is_string( $hook ) ) { # functions look like strings, too
 198                                 $func = $hook;
 199                         } else if ( is_object( $hook ) ) {
 200                                 $object = $hook_array[$event][$index];
 201                                 if ( $object instanceof Closure ) {
 202                                         $closure = true;
 203                                 } else {
 204                                         $method = "on" . $event;
 205                                 }
 206                         } else {
 207                                 throw new MWException( "Unknown datatype in hooks for " . $event . "\n" );
 208                         }
 209
 210                         /* We put the first data element on, if needed. */
 211
 212                         if ( $have_data ) {
 213                                 $hook_args = array_merge(array($data), $args);
 214                         } else {
 215                                 $hook_args = $args;
 216                         }
 217
 218                         if ( $closure ) {
 219                                 $callback = $object;
 220                                 $func = "hook-$event-closure";
 221                         } elseif ( isset( $object ) ) {
 222                                 $func = get_class( $object ) . '::' . $method;
 223                                 $callback = array( $object, $method );
 224                         } elseif ( false !== ( $pos = strpos( $func, '::' ) ) ) {
 225                                 $callback = array( substr( $func, 0, $pos ), substr( $func, $pos + 2 ) );
 226                         } else {
 227                                 $callback = $func;
 228                         }
 229
 230                         // Run autoloader (workaround for call_user_func_array bug)
 231                         is_callable( $callback );
 232
 233                         /* Call the hook. The documentation of call_user_func_array clearly
 234                          * states that FALSE is returned on failure. However this is not
 235                          * case always. In some version of PHP if the function signature
 236                          * does not match the call signature, PHP will issue an warning:
 237                          * Param y in x expected to be a reference, value given.
 238                          *
 239                          * In that case the call will also return null. The following code
 240                          * catches that warning and provides better error message. The
 241                          * function documentation also says that:
 242                          *     In other words, it does not depend on the function signature
 243                          *     whether the parameter is passed by a value or by a reference.
 244                          * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
 245                          * is unsurprisingly marked as bogus. In short handling of failures
 246                          * with call_user_func_array is a failure, the documentation for that
 247                          * function is wrong and misleading and PHP developers don't see any
 248                          * problem here.
 249                          */
 250                         $retval = null;
 251                         set_error_handler( array( 'Hooks', 'hookErrorHandler' ) );
 252                         wfProfileIn( $func );
 253                         try {
 254                                 $retval = call_user_func_array( $callback, $hook_args );
 255                         } catch ( MWHookException $e ) {
 256                                 $badhookmsg = $e->getMessage();
 257                         }
 258                         wfProfileOut( $func );
 259                         restore_error_handler();
 260
 261                         /* String return is an error; false return means stop processing. */
 262                         if ( is_string( $retval ) ) {
 263                                 global $wgOut;
 264                                 $wgOut->showFatalError( $retval );
 265                                 return false;
 266                         } elseif( $retval === null ) {
 267                                 if ( $closure ) {
 268                                         $prettyFunc = "$event closure";
 269                                 } elseif( is_array( $callback ) ) {
 270                                         if( is_object( $callback[0] ) ) {
 271                                                 $prettyClass = get_class( $callback[0] );
 272                                         } else {
 273                                                 $prettyClass = strval( $callback[0] );
 274                                         }
 275                                         $prettyFunc = $prettyClass . '::' . strval( $callback[1] );
 276                                 } else {
 277                                         $prettyFunc = strval( $callback );
 278                                 }
 279                                 if ( $badhookmsg ) {
 280                                         throw new MWException( "Detected bug in an extension! " .
 281                                         "Hook $prettyFunc has invalid call signature; " . $badhookmsg );
 282                                 } else {
 283                                         throw new MWException( "Detected bug in an extension! " .
 284                                                 "Hook $prettyFunc failed to return a value; " .
 285                                                 "should return true to continue hook processing or false to abort." );
 286                                 }
 287                         } else if ( !$retval ) {
 288                                 return false;
 289                         }
 290                 }
 291
 292                 return true;
 293         }
 294
 295         //This REALLY should be protected... but it's public for compatibility
 296         public static function hookErrorHandler( $errno, $errstr ) {
 297                 if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
 298                         throw new MWHookException( $errstr );
 299                 }
 300                 return false;
 301         }
 302 }