commit 7631e4b912531d9300c67c90fe69b4a921d5c0bd
Author: beejeebus <justin.p.randell@gmail.com>
Date:   Mon Apr 7 04:39:05 2014 +1000

    use serialize

diff --git a/core/lib/Drupal/Core/Cache/PhpBackend.php b/core/lib/Drupal/Core/Cache/PhpBackend.php
index f845ac0..0be649a 100644
--- a/core/lib/Drupal/Core/Cache/PhpBackend.php
+++ b/core/lib/Drupal/Core/Cache/PhpBackend.php
@@ -102,13 +102,6 @@ protected function prepareItem($cache, $allow_invalid) {
    * {@inheritdoc}
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = array()) {
-    if (is_object($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' => $data,
@@ -253,13 +246,12 @@ public function removeBin() {
    *   The cache item to store.
    */
   protected function writeItem($cid, array $item) {
-    $storage = $this->storage();
-    $data = var_export($item, TRUE);
-    $content =<<<EOF
-<?php
-return $data;
-EOF;
-    $storage->save($cid, $content);
+    $data = str_replace('\\', '\\\\', serialize($item));
+    $content = "<?php return unserialize(<<<EOF
+$data
+EOF
+);";
+    $this->storage()->save($cid, $content);
   }
 
   /**
diff --git a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
index e558816..4b20ea0 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericCacheBackendUnitTestBase.php
@@ -135,10 +135,11 @@ public function testSetGet() {
     $backend = $this->getCacheBackend();
 
     $this->assertIdentical(FALSE, $backend->get('test1'), "Backend does not contain data for cache id test1.");
-    $backend->set('test1', 7);
+    $with_backslash = array('foo' => '\Drupal\foo\Bar');
+    $backend->set('test1', $with_backslash);
     $cached = $backend->get('test1');
     $this->assert(is_object($cached), "Backend returned an object for cache id test1.");
-    $this->assertIdentical(7, $cached->data);
+    $this->assertIdentical($with_backslash, $cached->data);
     $this->assertTrue($cached->valid, 'Item is marked as valid.');
     $this->assertEqual($cached->created, REQUEST_TIME, 'Created time is correct.');
     $this->assertEqual($cached->expire, Cache::PERMANENT, 'Expire time is correct.');