diff -u b/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php b/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php
--- b/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/FileReadOnlyStorage.php
@@ -93,2 +93,20 @@
 
+  /**
+   * {@inheritdoc}
+   */
+  public function listAll() {
+    $names = array();
+    if (file_exists($this->directory)) {
+      foreach (new \DirectoryIterator($this->directory) as $fileinfo) {
+        if (!$fileinfo->isDot()) {
+          $name = $fileinfo->getFilename();
+          if ($name != '.htaccess') {
+            $names[] = $name;
+          }
+        }
+      }
+    }
+    return $names;
+  }
+
 }
diff -u b/core/lib/Drupal/Component/PhpStorage/FileStorage.php b/core/lib/Drupal/Component/PhpStorage/FileStorage.php
--- b/core/lib/Drupal/Component/PhpStorage/FileStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/FileStorage.php
@@ -191,13 +191,6 @@
   }
 
   /**
-   * {@inheritdoc}
-   */
-  public function getPath($name) {
-    return $this->getFullPath($name);
-  }
-
-  /**
    * Implements Drupal\Component\PhpStorage\PhpStorageInterface::writeable().
    */
   public function writeable() {
@@ -209,6 +202,13 @@
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function getPath($name) {
+    return $this->getFullPath($name);
+  }
+
+  /**
    * Implements Drupal\Component\PhpStorage\PhpStorageInterface::writeable().
    */
   public function writeable() {
@@ -257,2 +257,21 @@
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function listAll() {
+    $names = array();
+    if (file_exists($this->directory)) {
+      foreach (new \DirectoryIterator($this->directory) as $fileinfo) {
+        if (!$fileinfo->isDot()) {
+          $name = $fileinfo->getFilename();
+          if ($name != '.htaccess') {
+            $names[] = $name;
+          }
+        }
+      }
+    }
+    return $names;
+  }
+
 }
diff -u b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
--- b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
+++ b/core/lib/Drupal/Component/PhpStorage/PhpStorageInterface.php
@@ -93,2 +93,10 @@
 
+  /**
+   * Lists all the files in the storage.
+   *
+   * @return array
+   *   Array of filenames.
+   */
+  public function listAll();
+
 }
diff -u b/core/lib/Drupal/Core/Cache/PhpBackend.php b/core/lib/Drupal/Core/Cache/PhpBackend.php
--- b/core/lib/Drupal/Core/Cache/PhpBackend.php
+++ b/core/lib/Drupal/Core/Cache/PhpBackend.php
@@ -38,16 +38,19 @@
    */
   public function __construct($bin) {
     $this->bin = $bin;
-    $this->loadCache();
   }
 
   /**
    * {@inheritdoc}
    */
   public function get($cid, $allow_invalid = FALSE) {
-    $cids = array($cid);
-    $cache = $this->getMultiple($cids, $allow_invalid);
-    return reset($cache);
+    if ($file = $this->storage()->getPath($cid)) {
+      $cache = @include $file;
+    }
+    if (isset($cache)) {
+      return $this->prepareItem((object) $cache, $allow_invalid);
+    }
+    return FALSE;
   }
 
   /**
@@ -56,11 +59,8 @@
   public function getMultiple(&$cids, $allow_invalid = FALSE) {
     $ret = array();
 
-    $items = array_intersect_key($this->cache, array_flip($cids));
-
-    foreach ($items as $item) {
-      $item = $this->prepareItem($item, $allow_invalid);
-      if ($item) {
+    foreach ($cids as $cid) {
+      if ($item = $this->get($cid, $allow_invalid)) {
         $ret[$item->cid] = $item;
       }
     }
@@ -102,65 +102,67 @@
    * {@inheritdoc}
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = array()) {
-    $this->cache[$cid] = (object) array(
+    if (is_object($data) && !method_exists($data, '__set_state')) {
+      throw new \InvalidArgumentException(
+        "Invalid argument given, PhpBackend only allows objects that implement __set_state() " .
+        "and fully support var_export(). You can use the PhpBackend to save arbitrary object " .
+        "graphs using serialize()/unserialize()."
+      );
+    }
+    $item = array(
       'cid' => $cid,
       'data' => $data,
       'created' => REQUEST_TIME,
       'expire' => $expire,
       'tags' => $this->flattenTags($tags),
     );
-    $this->writeCache();
+    $this->writeItem($cid, $item);
   }
 
   /**
    * {@inheritdoc}
    */
   public function delete($cid) {
-    unset($this->cache[$cid]);
-    $this->writeCache();
+    $this->storage()->delete($cid);
   }
 
   /**
    * {@inheritdoc}
    */
   public function deleteMultiple(array $cids) {
-    $this->cache = array_diff_key($this->cache, array_flip($cids));
-    $this->writeCache();
+    foreach ($cids as $cid) {
+      $this->delete($cid);
+    }
   }
 
   /**
    * {@inheritdoc}
    */
   public function deleteTags(array $tags) {
-    $this->cache = array();
-    $this->writeCache();
-    return;
-
     $flat_tags = $this->flattenTags($tags);
-    foreach ($this->cache as $cid => $item) {
+    foreach ($this->storage()->listAll() as $cid) {
+      $item = $this->get($cid);
       if (array_intersect($flat_tags, $item->tags)) {
-        unset($this->cache[$cid]);
+        $this->delete($cid);
       }
     }
-    $this->writeCache();
   }
 
   /**
    * {@inheritdoc}
    */
   public function deleteAll() {
-    $this->cache = array();
-    $this->writeCache();
+    $this->storage()->deleteAll();
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidate($cid) {
-    if (isset($this->cache[$cid])) {
-      $this->cache[$cid]->expire = REQUEST_TIME - 1;
+    if ($item = $this->get($cid)) {
+      $item->expire = REQUEST_TIME - 1;
+      $this->writeItem($cid, (array) $item);
     }
-    $this->writeCache();
   }
 
   /**
@@ -168,40 +170,28 @@
    */
   public function invalidateMultiple(array $cids) {
     foreach ($cids as $cid) {
-      $this->cache[$cid]->expire = REQUEST_TIME - 1;
+      $this->invalidate($cid);
     }
-    $this->writeCache();
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidateTags(array $tags) {
-    $this->cache = array();
-    $this->writeCache();
-    return;
-
-    $change = FALSE;
     $flat_tags = $this->flattenTags($tags);
-    foreach ($this->cache as $cid => $item) {
-      if (array_intersect($flat_tags, $item->tags)) {
-        $this->cache[$cid]->expire = REQUEST_TIME - 1;
-        $change = TRUE;
+    foreach ($this->storage()->listAll() as $cid) {
+      $item = $this->get($cid);
+      if ($item && array_intersect($flat_tags, $item->tags)) {
+        $this->invalidate($cid);
       }
     }
-    if ($change) {
-      $this->writeCache();
-    }
   }
 
   /**
    * {@inheritdoc}
    */
   public function invalidateAll() {
-    foreach ($this->cache as $cid => $item) {
-      $this->cache[$cid]->expire = REQUEST_TIME - 1;
-    }
-    $this->writeCache();
+    $this->invalidateMultiple($this->storage()->listAll());
   }
 
   /**
@@ -236,7 +226,8 @@
    * {@inheritdoc}
    */
   public function isEmpty() {
-    return empty($this->cache);
+    $names = $this->storage()->listAll();
+    return empty($names);
   }
 
   /**
@@ -254,36 +245,21 @@
   }
 
   /**
-   * Writes the cache to PHP storage.
+   * Writes a cache item to PhpStorage.
+   *
+   * @param string $cid
+   *   The cache ID of the data to store.
+   * @param array $item
+   *   The cache item to store.
    */
-  protected function writeCache() {
+  protected function writeItem($cid, array $item) {
     $storage = $this->storage();
-    $data = Variable::export($this->cache);
+    $data = var_export($item, TRUE);
     $content =<<<EOF
 <?php
-\$cache = $data;
+return $data;
 EOF;
-    $storage->save($this->bin, $content);
-  }
-
-  /**
-   * Loads the cache from PHP storage.
-   */
-  protected function loadCache() {
-    $storage = $this->storage();
-
-    // Whether or not Drupal\Component\PhpStorage\PhpStorageInterface::getPath()
-    // checks for the existence of the file is an implementation of the storage.
-    if ($filename = $storage->getPath($this->bin)) {
-      // If this file exists it'll set a variable called $cache.
-      @include_once $filename;
-    }
-    if (isset($cache)) {
-      $this->cache = $cache;
-    }
-    else {
-      $this->cache = array();
-    }
+    $storage->save($cid, $content);
   }
 
   /**
@@ -293,7 +269,13 @@
    */
   protected function storage() {
     if (!isset($this->storage)) {
-      $this->storage = PhpStorageFactory::get('cache');
+      if ($this->bin != 'cache') {
+        $store = 'cache_' . $this->bin;
+      }
+      else {
+        $store = 'cache';
+      }
+      $this->storage = PhpStorageFactory::get($store);
     }
     return $this->storage;
   }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php
@@ -149,6 +149,17 @@ protected function getFullPath($name, &$directory = NULL, &$directory_mtime = NU
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function delete($name) {
+    $path = $this->getContainingDirectoryFullPath($name);
+    if (file_exists($path)) {
+      return $this->unlink($path);
+    }
+    return FALSE;
+  }
+
+  /**
    * Returns the full path of the containing directory where the file is or should be stored.
    */
   protected function getContainingDirectoryFullPath($name) {