diff --git a/src/MemcacheBackend.php b/src/MemcacheBackend.php
index da1bc43..836c801 100644
--- a/src/MemcacheBackend.php
+++ b/src/MemcacheBackend.php
@@ -102,7 +102,7 @@ class MemcacheBackend implements CacheBackendInterface {
    * {@inheritdoc}
    */
   public function getMultiple(&$cids, $allow_invalid = FALSE) {
-    $keys = array_map(function($cid) {
+    $keys = array_map(function ($cid) {
       return $this->key($cid);
     }, $cids);
 
@@ -117,7 +117,7 @@ class MemcacheBackend implements CacheBackendInterface {
         if ($result->data instanceof MultipartItem) {
           $childCIDs = $result->data->getCids();
           $dataParts = $this->memcache->getMulti($childCIDs);
-          if(count($dataParts) !== count($childCIDs)) {
+          if (count($dataParts) !== count($childCIDs)) {
             // We're missing a chunk of the original entry. It is not valid.
             continue;
           }
@@ -222,14 +222,14 @@ class MemcacheBackend implements CacheBackendInterface {
     $cache->checksum = $this->checksumProvider->getCurrentChecksum($tags);
 
     // Cache all items permanently. We handle expiration in our own logic.
-    if($this->memcache->set($this->key($cid), $cache)) {
+    if ($this->memcache->set($this->key($cid), $cache)) {
       return TRUE;
     }
 
     // Assume that the item is too large.  We need to split it into multiple
     // chunks with a parent entry referencing all the chunks.
     $childKeys = [];
-    foreach($this->splitItem($cache) as $part) {
+    foreach ($this->splitItem($cache) as $part) {
       $childKey = $this->key($part->cid);
 
       // If a single chunk fails to be set, stop trying - we can't reconstitute
diff --git a/src/MultipartItem.php b/src/MultipartItem.php
index a72fef6..63af183 100644
--- a/src/MultipartItem.php
+++ b/src/MultipartItem.php
@@ -3,14 +3,33 @@
 
 namespace Drupal\memcache;
 
-
+/**
+ * Wrapper for a split cache item.
+ *
+ * When a cache item is larger than Memcache can handle as a single item, it
+ * gets split into smaller chunks and stored as multiple items.  An object of
+ * this class gets stored with the original CID - it does not contain data
+ * itself, but tracks the CIDs of the children that contain the data.
+ */
 class MultipartItem {
   private $cids;
 
+  /**
+   * Constructor.
+   *
+   * @param string[] $cids
+   *   The CIDs that contain the item's data.
+   */
   public function __construct(array $cids) {
     $this->cids = $cids;
   }
 
+  /**
+   * Get the CIDs of this item's children.
+   *
+   * @return string[]
+   *   The CIDs that contain the item's data.
+   */
   public function getCids() {
     return $this->cids;
   }