includes/Hooks.php

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