diff -u b/includes/cache.inc b/includes/cache.inc
--- b/includes/cache.inc
+++ b/includes/cache.inc
@@ -1,15 +1,15 @@
 <?php
 
 /**
- * Factory for instantiating and statically caching the correct class for a cache bin.
+ * Factory for instantiating and statically caching the class for a cache bin.
  *
  * By default, this returns an instance of the DrupalDatabaseCache class.
- * Classes implementing DrupalCacheInterface can be used instead, either
- * as a default for all cache requests, or for specific bins.
+ * Classes implementing DrupalCacheInterface can be used instead, either as a
+ * default for all cache requests, or for specific bins.
  *
  * Configuration of cache bins should be done in settings.php
  *
- * For example to use 'MyCustomCache' for the''page' bin. Set the following
+ * For example, to use "MyCustomCache" for the "page" bin, set the following
  * variables:
  *
  * @code
@@ -21,8 +21,9 @@
  * @endcode
  *
  * Additionally, you can register your cache implementation to be used by
- * default for all cache bins by setting the variable 'cache_default_class' to
- * the name of your implementation of the DrupalCacheInterface, e.g.
+ * default for all cache bins by setting the variable "cache_default_class" to
+ * the name of your implementation of the DrupalCacheInterface.  For example:
+ *
  * @code
  * $conf['cache_default_class'] = 'MyCustomCache';
  * @endcode
@@ -30,6 +31,7 @@
  * @param $bin
  *   The cache bin for which the cache object should be returned, defaults to
  *   'cache'.
+ *
  * @return DrupalCacheInterface
  *   The cache object associated with the specified bin.
  */
@@ -60,10 +62,10 @@
 }
 
 /**
- * Interface for cache implementations.
+ * Provides the interface for cache implementations.
  *
  * All cache implementations have to implement this interface.
- * DrupalDatabaseCache provides the default implementation, which can be
+ * DrupalDatabaseCache provides the default implementation, which may be
  * consulted as an example.
  *
  * @see cache()
@@ -79,38 +81,40 @@
   function __construct($bin);
 
   /**
-   * Return data from the persistent cache. Data may be stored as either plain
-   * text or as serialized data. Will automatically return
-   * unserialized objects and arrays.
+   * Returns data from the persistent cache. Data may be stored as either plain
+   * text or as serialized data. Will automatically return unserialized objects
+   * and arrays.
    *
    * @param $cid
    *   The cache ID of the data to retrieve.
+   *
    * @return
    *   The cache or FALSE on failure.
    */
   function get($cid);
 
   /**
-   * Return data from the persistent cache when given an array of cache IDs.
+   * Returns data from the persistent cache when given an array of cache IDs.
    *
    * @param $cids
    *   An array of cache IDs for the data to retrieve. This is passed by
    *   reference, and will have the IDs successfully returned from cache
    *   removed.
+   *
    * @return
    *   An array of the items successfully returned from cache indexed by cid.
    */
    function getMultiple(&$cids);
 
   /**
-   * Store data in the persistent cache.
+   * Stores data in the persistent cache.
    *
    * @param $cid
    *   The cache ID of the data to store.
    * @param $data
    *   The data to store in the cache. Complex data types will be automatically
-   *   serialized before insertion.
-   *   Strings will be stored as plain text and not serialized.
+   *   serialized before insertion. Strings will be stored as plain text and not
+   *   serialized.
    * @param $expire
    *   One of the following values:
    *   - CACHE_PERMANENT: Indicates that the item should never be removed unless
@@ -123,7 +127,7 @@
   function set($cid, $data, $expire = CACHE_PERMANENT);
 
   /**
-   * Delete an item from the cache.
+   * Deletes an item from the cache.
    *
    * @param $cid
    *    The cache ID to delete.
@@ -131,7 +135,7 @@
   function delete($cid);
 
   /**
-   * Delete multiple items from the cache.
+   * Deletes multiple items from the cache.
    *
    * @param $cids
    *   An array of $cids to delete.
@@ -139,7 +143,7 @@
   function deleteMultiple(Array $cids);
 
   /**
-   * Delete items from the cache using a wildcard prefix.
+   * Deletes items from the cache using a wildcard prefix.
    *
    * @param $prefix
    *   A wildcard prefix.
@@ -147,34 +151,34 @@
   function deletePrefix($prefix);
 
   /**
-   * Flush all cache items in a bin.
+   * Flushes all cache items in a bin.
    */
   function flush();
 
   /**
-   * Expire temporary items from cache.
+   * Expires temporary items from cache.
    */
   function expire();
 
   /**
-   * Perform garbage collection on a cache bin.
+   * Performs garbage collection on a cache bin.
    */
   function garbageCollection();
 
   /**
-   * Check if a cache bin is empty.
+   * Checks whether a cache bin is empty.
    *
    * A cache bin is considered empty if it does not contain any valid data for
    * any cache ID.
    *
    * @return
-   *   TRUE if the cache bin specified is empty.
+   *   TRUE if the cache bin is empty; FALSE otherwise.
    */
   function isEmpty();
 }
 
 /**
- * Default cache implementation.
+ * Provides the default cache implementation.
  *
  * This is Drupal's default cache implementation. It uses the database to store
  * cached data. Each cache bin corresponds to a database table by the same name.
@@ -183,8 +187,8 @@
   protected $bin;
 
   function __construct($bin) {
-    // All cache tables should be prefixed with 'cache_', apart from the
-    // default 'cache' bin, which would look silly.
+    // All cache tables should be prefixed with 'cache_', except for the
+    // default 'cache' bin.
     if ($bin != 'cache') {
       $bin = 'cache_' . $bin;
     }
@@ -228,7 +232,7 @@
   }
 
   /**
-   * Prepare a cached item.
+   * Prepares a cached item.
    *
    * Checks that items are either permanent or did not expire, and unserializes
    * data as appropriate.
@@ -249,9 +253,9 @@
     // If enforcing a minimum cache lifetime, validate that the data is
     // currently valid for this user before we return it by making sure the cache
     // entry was created before the timestamp in the current session's cache
-    // timer. The cache variable is loaded into the $user object by _drupal_session_read()
-    // in session.inc. If the data is permanent or we're not enforcing a minimum
-    // cache lifetime always return the cached data.
+    // timer. The cache variable is loaded into the $user object by
+    // _drupal_session_read() in session.inc. If the data is permanent or we're
+    // not enforcing a minimum cache lifetime always return the cached data.
     if ($cache->expire != CACHE_PERMANENT && variable_get('cache_lifetime', 0) && $user->cache > $cache->created) {
       // This cache data is too old and thus not valid for us, ignore it.
       return FALSE;
@@ -326,12 +330,12 @@
 
       $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
       if ($cache_flush == 0) {
-        // This is the first request to clear the cache, start a timer.
+        // This is the first request to clear the cache; start a timer.
         variable_set('cache_flush_' . $this->bin, REQUEST_TIME);
       }
       elseif (REQUEST_TIME > ($cache_flush + variable_get('cache_lifetime', 0))) {
-        // Clear the cache for everyone, cache_lifetime seconds have
-        // passed since the first request to clear the cache.
+        // Clear the cache for everyone; cache_lifetime seconds have passed
+        // since the first request to clear the cache.
         db_delete($this->bin)
           ->condition('expire', CACHE_PERMANENT, '<>')
           ->condition('expire', REQUEST_TIME, '<')
@@ -340,7 +344,7 @@
       }
     }
     else {
-      // No minimum cache lifetime, flush all temporary cache entries now.
+      // No minimum cache lifetime; flush all temporary cache entries now.
       db_delete($this->bin)
         ->condition('expire', CACHE_PERMANENT, '<>')
         ->condition('expire', REQUEST_TIME, '<')
@@ -355,7 +359,8 @@
     // often since this will remove temporary cache items indiscriminately.
     $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
     if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= REQUEST_TIME)) {
-      // Reset the variable immediately to prevent a meltdown in heavy load situations.
+      // Reset the variable immediately to prevent a meltdown in heavy load
+      // situations.
       variable_set('cache_flush_' . $this->bin, 0);
       // Time to flush old cache data
       db_delete($this->bin)