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   1  <?php
   2  
   3  /**
   4   * @file
   5   * Controls the boxes that are displayed around the main content.
   6   */
   7  
   8  /**
   9   * Denotes that a block is not enabled in any region and should not
  10   * be shown.
  11   */
  12  define('BLOCK_REGION_NONE', -1);
  13  
  14  /**
  15   * Constants defining cache granularity for blocks.
  16   *
  17   * Modules specify the caching patterns for their blocks using binary
  18   * combinations of these constants in their hook_block(op 'list'):
  19   *   $block[delta]['cache'] = BLOCK_CACHE_PER_ROLE | BLOCK_CACHE_PER_PAGE;
  20   * BLOCK_CACHE_PER_ROLE is used as a default when no caching pattern is
  21   * specified.
  22   *
  23   * The block cache is cleared in cache_clear_all(), and uses the same clearing
  24   * policy than page cache (node, comment, user, taxonomy added or updated...).
  25   * Blocks requiring more fine-grained clearing might consider disabling the
  26   * built-in block cache (BLOCK_NO_CACHE) and roll their own.
  27   *
  28   * Note that user 1 is excluded from block caching.
  29   */
  30  
  31  /**
  32   * The block should not get cached. This setting should be used:
  33   * - for simple blocks (notably those that do not perform any db query),
  34   * where querying the db cache would be more expensive than directly generating
  35   * the content.
  36   * - for blocks that change too frequently.
  37   */
  38  define('BLOCK_NO_CACHE', -1);
  39  
  40  /**
  41   * The block can change depending on the roles the user viewing the page belongs to.
  42   * This is the default setting, used when the block does not specify anything.
  43   */
  44  define('BLOCK_CACHE_PER_ROLE', 0x0001);
  45  
  46  /**
  47   * The block can change depending on the user viewing the page.
  48   * This setting can be resource-consuming for sites with large number of users,
  49   * and thus should only be used when BLOCK_CACHE_PER_ROLE is not sufficient.
  50   */
  51  define('BLOCK_CACHE_PER_USER', 0x0002);
  52  
  53  /**
  54   * The block can change depending on the page being viewed.
  55   */
  56  define('BLOCK_CACHE_PER_PAGE', 0x0004);
  57  
  58  /**
  59   * The block is the same for every user on every page where it is visible.
  60   */
  61  define('BLOCK_CACHE_GLOBAL', 0x0008);
  62  
  63  /**
  64   * Implementation of hook_help().
  65   */
  66  function block_help($path, $arg) {
  67    switch ($path) {
  68      case 'admin/help#block':
  69        $output = '<p>'. t('Blocks are boxes of content rendered into an area, or region, of a web page. The default theme Garland, for example, implements the regions "left sidebar", "right sidebar", "content", "header", and "footer", and a block may appear in any one of these areas. The <a href="@blocks">blocks administration page</a> provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions.', array('@blocks' => url('admin/build/block'))) .'</p>';
  70        $output .= '<p>'. t('Although blocks are usually generated automatically by modules (like the <em>User login</em> block, for example), administrators can also define custom blocks. Custom blocks have a title, description, and body. The body of the block can be as long as necessary, and can contain content supported by any available <a href="@input-format">input format</a>.', array('@input-format' => url('admin/settings/filters'))) .'</p>';
  71        $output .= '<p>'. t('When working with blocks, remember that:') .'</p>';
  72        $output .= '<ul><li>'. t('since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis.') .'</li>';
  73        $output .= '<li>'. t('disabled blocks, or blocks not in a region, are never shown.') .'</li>';
  74        $output .= '<li>'. t('when throttle module is enabled, throttled blocks (blocks with the <em>Throttle</em> checkbox selected) are hidden during high server loads.') .'</li>';
  75        $output .= '<li>'. t('blocks can be configured to be visible only on certain pages.') .'</li>';
  76        $output .= '<li>'. t('blocks can be configured to be visible only when specific conditions are true.') .'</li>';
  77        $output .= '<li>'. t('blocks can be configured to be visible only for certain user roles.') .'</li>';
  78        $output .= '<li>'. t('when allowed by an administrator, specific blocks may be enabled or disabled on a per-user basis using the <em>My account</em> page.') .'</li>';
  79        $output .= '<li>'. t('some dynamic blocks, such as those generated by modules, will be displayed only on certain pages.') .'</li></ul>';
  80        $output .= '<p>'. t('For more information, see the online handbook entry for <a href="@block">Block module</a>.', array('@block' => 'http://drupal.org/handbook/modules/block/')) .'</p>';
  81        return $output;
  82      case 'admin/build/block':
  83        $throttle = module_exists('throttle');
  84        $output = '<p>'. t('This page provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions. To change the region or order of a block, grab a drag-and-drop handle under the <em>Block</em> column and drag the block to a new location in the list. (Grab a handle by clicking and holding the mouse while hovering over a handle icon.) Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. Remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page.') .'</p>';
  85        if ($throttle) {
  86          $output .= '<p>'. t('To reduce CPU usage, database traffic or bandwidth, blocks may be automatically disabled during high server loads by selecting their <em>Throttle</em> checkbox. Adjust throttle thresholds on the <a href="@throttleconfig">throttle configuration page</a>.', array('@throttleconfig' => url('admin/settings/throttle'))) .'</p>';
  87        }
  88        $output .= '<p>'. t('Click the <em>configure</em> link next to each block to configure its specific title and visibility settings. Use the <a href="@add-block">add block page</a> to create a custom block.', array('@add-block' => url('admin/build/block/add'))) .'</p>';
  89        return $output;
  90      case 'admin/build/block/add':
  91        return '<p>'. t('Use this page to create a new custom block. New blocks are disabled by default, and must be moved to a region on the <a href="@blocks">blocks administration page</a> to be visible.', array('@blocks' => url('admin/build/block'))) .'</p>';
  92    }
  93  }
  94  
  95  /**
  96   * Implementation of hook_theme()
  97   */
  98  function block_theme() {
  99    return array(
 100      'block_admin_display_form' => array(
 101        'template' => 'block-admin-display-form',
 102        'file' => 'block.admin.inc',
 103        'arguments' => array('form' => NULL),
 104      ),
 105    );
 106  }
 107  
 108  /**
 109   * Implementation of hook_perm().
 110   */
 111  function block_perm() {
 112    return array('administer blocks', 'use PHP for block visibility');
 113  }
 114  
 115  /**
 116   * Implementation of hook_menu().
 117   */
 118  function block_menu() {
 119    $items['admin/build/block'] = array(
 120      'title' => 'Blocks',
 121      'description' => 'Configure what block content appears in your site\'s sidebars and other regions.',
 122      'page callback' => 'block_admin_display',
 123      'access arguments' => array('administer blocks'),
 124      'file' => 'block.admin.inc',
 125    );
 126    $items['admin/build/block/list'] = array(
 127      'title' => 'List',
 128      'type' => MENU_DEFAULT_LOCAL_TASK,
 129      'weight' => -10,
 130    );
 131    $items['admin/build/block/list/js'] = array(
 132      'title' => 'JavaScript List Form',
 133      'page callback' => 'block_admin_display_js',
 134      'access arguments' => array('administer blocks'),
 135      'type' => MENU_CALLBACK,
 136      'file' => 'block.admin.inc',
 137    );
 138    $items['admin/build/block/configure'] = array(
 139      'title' => 'Configure block',
 140      'page callback' => 'drupal_get_form',
 141      'page arguments' => array('block_admin_configure'),
 142      'access arguments' => array('administer blocks'),
 143      'type' => MENU_CALLBACK,
 144      'file' => 'block.admin.inc',
 145    );
 146    $items['admin/build/block/delete'] = array(
 147      'title' => 'Delete block',
 148      'page callback' => 'drupal_get_form',
 149      'page arguments' => array('block_box_delete'),
 150      'access arguments' => array('administer blocks'),
 151      'type' => MENU_CALLBACK,
 152      'file' => 'block.admin.inc',
 153    );
 154    $items['admin/build/block/add'] = array(
 155      'title' => 'Add block',
 156      'page callback' => 'drupal_get_form',
 157      'page arguments' => array('block_add_block_form'),
 158      'access arguments' => array('administer blocks'),
 159      'type' => MENU_LOCAL_TASK,
 160      'file' => 'block.admin.inc',
 161    );
 162    $default = variable_get('theme_default', 'garland');
 163    foreach (list_themes() as $key => $theme) {
 164      $items['admin/build/block/list/'. $key] = array(
 165        'title' => check_plain($theme->info['name']),
 166        'page arguments' => array($key),
 167        'type' => $key == $default ? MENU_DEFAULT_LOCAL_TASK : MENU_LOCAL_TASK,
 168        'weight' => $key == $default ? -10 : 0,
 169        'file' => 'block.admin.inc',
 170        'access callback' => '_block_themes_access',
 171        'access arguments' => array($theme),
 172      );
 173    }
 174    return $items;
 175  }
 176  
 177  /**
 178   * Menu item access callback - only admin or enabled themes can be accessed
 179   */
 180  function _block_themes_access($theme) {
 181    return user_access('administer blocks') && ($theme->status || $theme->name == variable_get('admin_theme', '0'));
 182  }
 183  
 184  /**
 185   * Implementation of hook_block().
 186   *
 187   * Generates the administrator-defined blocks for display.
 188   */
 189  function block_block($op = 'list', $delta = 0, $edit = array()) {
 190    switch ($op) {
 191      case 'list':
 192        $blocks = array();
 193  
 194        $result = db_query('SELECT bid, info FROM {boxes} ORDER BY info');
 195        while ($block = db_fetch_object($result)) {
 196          $blocks[$block->bid]['info'] = $block->info;
 197          // Not worth caching.
 198          $blocks[$block->bid]['cache'] = BLOCK_NO_CACHE;
 199        }
 200        return $blocks;
 201  
 202      case 'configure':
 203        $box = array('format' => FILTER_FORMAT_DEFAULT);
 204        if ($delta) {
 205          $box = block_box_get($delta);
 206        }
 207        if (filter_access($box['format'])) {
 208          return block_box_form($box);
 209        }
 210        break;
 211  
 212      case 'save':
 213        block_box_save($edit, $delta);
 214        break;
 215  
 216      case 'view':
 217        $block = db_fetch_object(db_query('SELECT body, format FROM {boxes} WHERE bid = %d', $delta));
 218        $data['content'] = check_markup($block->body, $block->format, FALSE);
 219        return $data;
 220    }
 221  }
 222  
 223  /**
 224   * Update the 'blocks' DB table with the blocks currently exported by modules.
 225   *
 226   * @param $theme
 227   *   The theme to rehash blocks for. If not provided, defaults to the currently
 228   *   used theme.
 229   *
 230   * @return
 231   *   Blocks currently exported by modules.
 232   */
 233  function _block_rehash($theme = NULL) {
 234    global $theme_key;
 235  
 236    init_theme();
 237    if (!isset($theme)) {
 238      $theme = $theme_key;
 239    }
 240  
 241    $result = db_query("SELECT * FROM {blocks} WHERE theme = '%s'", $theme);
 242    $old_blocks = array();
 243    while ($old_block = db_fetch_array($result)) {
 244      $old_blocks[$old_block['module']][$old_block['delta']] = $old_block;
 245    }
 246  
 247    $blocks = array();
 248    // Valid region names for the theme.
 249    $regions = system_region_list($theme);
 250  
 251    foreach (module_list() as $module) {
 252      $module_blocks = module_invoke($module, 'block', 'list');
 253      if ($module_blocks) {
 254        foreach ($module_blocks as $delta => $block) {
 255          if (empty($old_blocks[$module][$delta])) {
 256            // If it's a new block, add identifiers.
 257            $block['module'] = $module;
 258            $block['delta']  = $delta;
 259            $block['theme']  = $theme;
 260            if (!isset($block['pages'])) {
 261              // {block}.pages is type 'text', so it cannot have a
 262              // default value, and not null, so we need to provide
 263              // value if the module did not.
 264              $block['pages']  = '';
 265            }
 266            // Add defaults and save it into the database.
 267            drupal_write_record('blocks', $block);
 268            // Set region to none if not enabled.
 269            $block['region'] = $block['status'] ? $block['region'] : BLOCK_REGION_NONE;
 270            // Add to the list of blocks we return.
 271            $blocks[] = $block;
 272          }
 273          else {
 274            // If it's an existing block, database settings should overwrite
 275            // the code. The only exceptions are 'cache' which is only definable
 276            // and updatable in the code, and 'info' which is not stored in
 277            // the database.
 278            // Update the cache mode only; the other values don't need to change.
 279            if (isset($block['cache']) && $block['cache'] != $old_blocks[$module][$delta]['cache']) {
 280              db_query("UPDATE {blocks} SET cache = %d WHERE bid = %d", $block['cache'], $old_blocks[$module][$delta]['bid']);
 281            }
 282            // Add 'info' to this block.
 283            $old_blocks[$module][$delta]['info'] = $block['info'];
 284            // If the region name does not exist, disable the block and assign it to none.
 285            if (!empty($old_blocks[$module][$delta]['region']) && !isset($regions[$old_blocks[$module][$delta]['region']])) {
 286              drupal_set_message(t('The block %info was assigned to the invalid region %region and has been disabled.', array('%info' => $old_blocks[$module][$delta]['info'], '%region' => $old_blocks[$module][$delta]['region'])), 'warning');
 287              $old_blocks[$module][$delta]['status'] = 0;
 288              $old_blocks[$module][$delta]['region'] = BLOCK_REGION_NONE;
 289            }
 290            else {
 291              $old_blocks[$module][$delta]['region'] = $old_blocks[$module][$delta]['status'] ? $old_blocks[$module][$delta]['region'] : BLOCK_REGION_NONE;
 292            }
 293            // Add this block to the list of blocks we return.
 294            $blocks[] = $old_blocks[$module][$delta];
 295            // Remove this block from the list of blocks to be deleted.
 296            unset($old_blocks[$module][$delta]);
 297          }
 298        }
 299      }
 300    }
 301  
 302    // Remove blocks that are no longer defined by the code from the database.
 303    foreach ($old_blocks as $module => $old_module_blocks) {
 304      // This cleanup does not apply to disabled modules, to avoid configuration
 305      // being lost when modules are disabled.
 306      if (module_exists($module)) {
 307        foreach ($old_module_blocks as $delta => $block) {
 308          db_query("DELETE FROM {blocks} WHERE module = '%s' AND delta = '%s' AND theme = '%s'", $module, $delta, $theme);
 309        }
 310      }
 311    }
 312    return $blocks;
 313  }
 314  
 315  /**
 316   * Implementation of hook_flush_caches().
 317   */
 318  function block_flush_caches() {
 319    // Rehash blocks for active themes. We don't use list_themes() here,
 320    // because if MAINTENANCE_MODE is defined it skips reading the database,
 321    // and we can't tell which themes are active.
 322    $result = db_query("SELECT name FROM {system} WHERE type = 'theme' AND status = 1");
 323    while ($theme = db_result($result)) {
 324      _block_rehash($theme);
 325    }
 326  }
 327  
 328  /**
 329   * Returns information from database about a user-created (custom) block.
 330   *
 331   * @param $bid
 332   *   ID of the block to get information for.
 333   * @return
 334   *   Associative array of information stored in the database for this block.
 335   *   Array keys:
 336   *   - bid: Block ID.
 337   *   - info: Block description.
 338   *   - body: Block contents.
 339   *   - format: Filter ID of the filter format for the body.
 340   */
 341  function block_box_get($bid) {
 342    return db_fetch_array(db_query("SELECT * FROM {boxes} WHERE bid = %d", $bid));
 343  }
 344  
 345  /**
 346   * Define the custom block form.
 347   */
 348  function block_box_form($edit = array()) {
 349    $edit += array(
 350      'info' => '',
 351      'body' => '',
 352    );
 353    $form['info'] = array(
 354      '#type' => 'textfield',
 355      '#title' => t('Block description'),
 356      '#default_value' => $edit['info'],
 357      '#maxlength' => 64,
 358      '#description' => t('A brief description of your block. Used on the <a href="@overview">block overview page</a>.', array('@overview' => url('admin/build/block'))),
 359      '#required' => TRUE,
 360      '#weight' => -19,
 361    );
 362    $form['body_field']['#weight'] = -17;
 363    $form['body_field']['body'] = array(
 364      '#type' => 'textarea',
 365      '#title' => t('Block body'),
 366      '#default_value' => $edit['body'],
 367      '#rows' => 15,
 368      '#description' => t('The content of the block as shown to the user.'),
 369      '#weight' => -17,
 370    );
 371    if (!isset($edit['format'])) {
 372      $edit['format'] = FILTER_FORMAT_DEFAULT;
 373    }
 374    $form['body_field']['format'] = filter_form($edit['format'], -16);
 375  
 376    return $form;
 377  }
 378  
 379  /**
 380   * Saves a user-created block in the database.
 381   *
 382   * @param $edit
 383   *   Associative array of fields to save. Array keys:
 384   *   - info: Block description.
 385   *   - body: Block contents.
 386   *   - format: Filter ID of the filter format for the body.
 387   * @param $delta
 388   *   Block ID of the block to save.
 389   * @return
 390   *   Always returns TRUE.
 391   */
 392  function block_box_save($edit, $delta) {
 393    if (!filter_access($edit['format'])) {
 394      $edit['format'] = FILTER_FORMAT_DEFAULT;
 395    }
 396  
 397    db_query("UPDATE {boxes} SET body = '%s', info = '%s', format = %d WHERE bid = %d", $edit['body'], $edit['info'], $edit['format'], $delta);
 398  
 399    return TRUE;
 400  }
 401  
 402  /**
 403   * Implementation of hook_user().
 404   *
 405   * Allow users to decide which custom blocks to display when they visit
 406   * the site.
 407   */
 408  function block_user($type, $edit, &$account, $category = NULL) {
 409    switch ($type) {
 410      case 'form':
 411        if ($category == 'account') {
 412          $rids = array_keys($account->roles);
 413          $result = db_query("SELECT DISTINCT b.* FROM {blocks} b LEFT JOIN {blocks_roles} r ON b.module = r.module AND b.delta = r.delta WHERE b.status = 1 AND b.custom != 0 AND (r.rid IN (". db_placeholders($rids) .") OR r.rid IS NULL) ORDER BY b.weight, b.module", $rids);
 414          $form['block'] = array('#type' => 'fieldset', '#title' => t('Block configuration'), '#weight' => 3, '#collapsible' => TRUE, '#tree' => TRUE);
 415          while ($block = db_fetch_object($result)) {
 416            $data = module_invoke($block->module, 'block', 'list');
 417            if ($data[$block->delta]['info']) {
 418              $return = TRUE;
 419              $form['block'][$block->module][$block->delta] = array('#type' => 'checkbox', '#title' => check_plain($data[$block->delta]['info']), '#default_value' => isset($account->block[$block->module][$block->delta]) ? $account->block[$block->module][$block->delta] : ($block->custom == 1));
 420            }
 421          }
 422  
 423          if (!empty($return)) {
 424            return $form;
 425          }
 426        }
 427  
 428        break;
 429      case 'validate':
 430        if (empty($edit['block'])) {
 431          $edit['block'] = array();
 432        }
 433        return $edit;
 434    }
 435  }
 436  
 437  /**
 438   * Return all blocks in the specified region for the current user.
 439   *
 440   * @param $region
 441   *   The name of a region.
 442   *
 443   * @return
 444   *   An array of block objects, indexed with module name and block delta
 445   *   concatenated with an underscore, thus: MODULE_DELTA. If you are displaying
 446   *   your blocks in one or two sidebars, you may check whether this array is
 447   *   empty to see how many columns are going to be displayed.
 448   *
 449   * @todo
 450   *   Now that the blocks table has a primary key, we should use that as the
 451   *   array key instead of MODULE_DELTA.
 452   */
 453  function block_list($region) {
 454    global $user, $theme_key;
 455  
 456    static $blocks = array();
 457  
 458    if (!count($blocks)) {
 459      $rids = array_keys($user->roles);
 460      $result = db_query(db_rewrite_sql("SELECT DISTINCT b.* FROM {blocks} b LEFT JOIN {blocks_roles} r ON b.module = r.module AND b.delta = r.delta WHERE b.theme = '%s' AND b.status = 1 AND (r.rid IN (". db_placeholders($rids) .") OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module", 'b', 'bid'), array_merge(array($theme_key), $rids));
 461      while ($block = db_fetch_object($result)) {
 462        if (!isset($blocks[$block->region])) {
 463          $blocks[$block->region] = array();
 464        }
 465        // Use the user's block visibility setting, if necessary
 466        if ($block->custom != 0) {
 467          if ($user->uid && isset($user->block[$block->module][$block->delta])) {
 468            $enabled = $user->block[$block->module][$block->delta];
 469          }
 470          else {
 471            $enabled = ($block->custom == 1);
 472          }
 473        }
 474        else {
 475          $enabled = TRUE;
 476        }
 477  
 478        // Match path if necessary
 479        if ($block->pages) {
 480          if ($block->visibility < 2) {
 481            $path = drupal_get_path_alias($_GET['q']);
 482            // Compare with the internal and path alias (if any).
 483            $page_match = drupal_match_path($path, $block->pages);
 484            if ($path != $_GET['q']) {
 485              $page_match = $page_match || drupal_match_path($_GET['q'], $block->pages);
 486            }
 487            // When $block->visibility has a value of 0, the block is displayed on
 488            // all pages except those listed in $block->pages. When set to 1, it
 489            // is displayed only on those pages listed in $block->pages.
 490            $page_match = !($block->visibility xor $page_match);
 491          }
 492          else {
 493            $page_match = drupal_eval($block->pages);
 494          }
 495        }
 496        else {
 497          $page_match = TRUE;
 498        }
 499        $block->enabled = $enabled;
 500        $block->page_match = $page_match;
 501        $blocks[$block->region]["{$block->module}_{$block->delta}"] = $block;
 502      }
 503    }
 504  
 505    // Create an empty array if there were no entries
 506    if (!isset($blocks[$region])) {
 507      $blocks[$region] = array();
 508    }
 509  
 510    foreach ($blocks[$region] as $key => $block) {
 511      // Render the block content if it has not been created already.
 512      if (!isset($block->content)) {
 513        // Erase the block from the static array - we'll put it back if it has content.
 514        unset($blocks[$region][$key]);
 515        if ($block->enabled && $block->page_match) {
 516          // Check the current throttle status and see if block should be displayed
 517          // based on server load.
 518          if (!($block->throttle && (module_invoke('throttle', 'status') > 0))) {
 519            // Try fetching the block from cache. Block caching is not compatible with
 520            // node_access modules. We also preserve the submission of forms in blocks,
 521            // by fetching from cache only if the request method is 'GET'.
 522            if (!count(module_implements('node_grants')) && $_SERVER['REQUEST_METHOD'] == 'GET' && ($cid = _block_get_cache_id($block)) && ($cache = cache_get($cid, 'cache_block'))) {
 523              $array = $cache->data;
 524            }
 525            else {
 526              $array = module_invoke($block->module, 'block', 'view', $block->delta);
 527              if (isset($cid)) {
 528                cache_set($cid, $array, 'cache_block', CACHE_TEMPORARY);
 529              }
 530            }
 531  
 532            if (isset($array) && is_array($array)) {
 533              foreach ($array as $k => $v) {
 534                $block->$k = $v;
 535              }
 536            }
 537          }
 538          if (isset($block->content) && $block->content) {
 539            // Override default block title if a custom display title is present.
 540            if ($block->title) {
 541              // Check plain here to allow module generated titles to keep any markup.
 542              $block->subject = $block->title == '<none>' ? '' : check_plain($block->title);
 543            }
 544            if (!isset($block->subject)) {
 545              $block->subject = '';
 546            }
 547            $blocks[$block->region]["{$block->module}_{$block->delta}"] = $block;
 548          }
 549        }
 550      }
 551    }
 552    return $blocks[$region];
 553  }
 554  
 555  /**
 556   * Assemble the cache_id to use for a given block.
 557   *
 558   * The cache_id string reflects the viewing context for the current block
 559   * instance, obtained by concatenating the relevant context information
 560   * (user, page, ...) according to the block's cache settings (BLOCK_CACHE_*
 561   * constants). Two block instances can use the same cached content when
 562   * they share the same cache_id.
 563   *
 564   * Theme and language contexts are automatically differenciated.
 565   *
 566   * @param $block
 567   * @return
 568   *   The string used as cache_id for the block.
 569   */
 570  function _block_get_cache_id($block) {
 571    global $theme, $base_root, $user;
 572  
 573    // User 1 being out of the regular 'roles define permissions' schema,
 574    // it brings too many chances of having unwanted output get in the cache
 575    // and later be served to other users. We therefore exclude user 1 from
 576    // block caching.
 577    if (variable_get('block_cache', 0) && $block->cache != BLOCK_NO_CACHE && $user->uid != 1) {
 578      $cid_parts = array();
 579  
 580      // Start with common sub-patterns: block identification, theme, language.
 581      $cid_parts[] = $block->module;
 582      $cid_parts[] = $block->delta;
 583      $cid_parts[] = $theme;
 584      if (module_exists('locale')) {
 585        global $language;
 586        $cid_parts[] = $language->language;
 587      }
 588  
 589      // 'PER_ROLE' and 'PER_USER' are mutually exclusive. 'PER_USER' can be a
 590      // resource drag for sites with many users, so when a module is being
 591      // equivocal, we favor the less expensive 'PER_ROLE' pattern.
 592      if ($block->cache & BLOCK_CACHE_PER_ROLE) {
 593        $cid_parts[] = 'r.'. implode(',', array_keys($user->roles));
 594      }
 595      elseif ($block->cache & BLOCK_CACHE_PER_USER) {
 596        $cid_parts[] = "u.$user->uid";
 597      }
 598  
 599      if ($block->cache & BLOCK_CACHE_PER_PAGE) {
 600        $cid_parts[] = $base_root . request_uri();
 601      }
 602  
 603      return implode(':', $cid_parts);
 604    }
 605  }