diff --git a/src/LeanCloud/Client.php b/src/LeanCloud/Client.php
index 1ed250d..b9a7719 100644
--- a/src/LeanCloud/Client.php
+++ b/src/LeanCloud/Client.php
@@ -400,6 +400,7 @@ public static function request($method, $path, $data,
         }
         $reqId = rand(100,999);
         if (self::$debugMode) {
+            error_log("[DEBUG] HEADERS {$reqId}:" . json_encode($headersList));
             error_log("[DEBUG] REQUEST {$reqId}: {$method} {$url} {$json}");
         }
         $resp     = curl_exec($req);
diff --git a/src/LeanCloud/Object.php b/src/LeanCloud/Object.php
index a302758..be8df91 100644
--- a/src/LeanCloud/Object.php
+++ b/src/LeanCloud/Object.php
@@ -13,6 +13,8 @@
  *
  */
 class Object {
+
+    const PRESERVED_KEYS = array("objectId", "updatedAt", "createdAt");
     /**
      * Map of registered className to class.
      *
@@ -141,15 +143,15 @@ public function getClassName() {
     }
 
     public function disableBeforeHook() {
-        $this->set("__before",
-                   Client::signHook("__before_for_{$this->getClassName()}",
-                                        round(microtime(true) * 1000)));
+        $this->_set("__before",
+                    Client::signHook("__before_for_{$this->getClassName()}",
+                                     round(microtime(true) * 1000)));
     }
 
     public function disableAfterHook() {
-        $this->set("__after",
-                   Client::signHook("__after_for_{$this->getClassName()}",
-                                        round(microtime(true) * 1000)));
+        $this->_set("__after",
+                    Client::signHook("__after_for_{$this->getClassName()}",
+                                     round(microtime(true) * 1000)));
     }
 
     /**
@@ -230,6 +232,18 @@ public function getUpdatedAt() {
         return $this->get("updatedAt");
     }
 
+    private function _set($key, $val) {
+        if ($key === "ACL" &&
+            !($val instanceof ACL)) {
+            throw new RuntimeException("Invalid ACL.");
+        }
+        if (!($val instanceof IOperation)) {
+            $val = new SetOperation($key, $val);
+        }
+        $this->_applyOperation($val);
+        return $this;
+    }
+
     /**
      * Set field value by key
      *
@@ -239,14 +253,10 @@ public function getUpdatedAt() {
      * @throws RuntimeException
      */
     public function set($key, $val) {
-        if (in_array($key, array("objectId", "createdAt", "updatedAt"))) {
+        if (in_array($key, self::PRESERVED_KEYS)) {
             throw new \RuntimeException("Preserved field could not be set.");
         }
-        if (!($val instanceof IOperation)) {
-            $val = new SetOperation($key, $val);
-        }
-        $this->_applyOperation($val);
-        return $this;
+        return $this->_set($key, $val);
     }
 
     /**
@@ -256,7 +266,7 @@ public function set($key, $val) {
      * @return self
      */
     public function setACL(ACL $acl) {
-        return $this->set("ACL", $acl);
+        return $this->_set("ACL", $acl);
     }
 
     /**
diff --git a/src/LeanCloud/User.php b/src/LeanCloud/User.php
index e5e1da7..377bb1d 100644
--- a/src/LeanCloud/User.php
+++ b/src/LeanCloud/User.php
@@ -232,6 +232,53 @@ private static function clearCurrentUser() {
         self::setCurrentSessionToken(null);
     }
 
+    /**
+     * Refresh session token
+     */
+    public function refreshSessionToken() {
+        $resp = Client::put("/users/{$this->getObjectId()}/refreshSessionToken",
+                            null);
+        $this->mergeAfterFetch($resp);
+        static::saveCurrentUser($this);
+    }
+
+    /**
+     * Test if user logged in and session token is valid.
+     *
+     * @return bool
+     */
+    public function isAuthenticated() {
+        $token = $this->getSessionToken();
+        if (!$token) {
+            return false;
+        }
+        try {
+            $resp = Client::get("/users/me",
+                                array("session_token" => $token));
+        } catch(CloudException $ex) {
+            if ($ex->getCode() === 211) {
+                return false;
+            }
+            throw ex;
+        }
+        return true;
+    }
+
+    /**
+     * Get roles the user belongs to
+     *
+     * @return array Array of Role
+     */
+    public function getRoles() {
+        if (!$this->getObjectId()) {
+            return array();
+        }
+        $query = new Query("_Role");
+        $query->equalTo("users", $this);
+        $roles = $query->find();
+        return $roles;
+    }
+
     /**
      * Log-in user by session token
      *
diff --git a/test/UserTest.php b/test/UserTest.php
index e22b5c0..1023802 100644
--- a/test/UserTest.php
+++ b/test/UserTest.php
@@ -2,6 +2,8 @@
 
 use LeanCloud\Client;
 use LeanCloud\User;
+use LeanCloud\Role;
+use LeanCloud\ACL;
 use LeanCloud\File;
 use LeanCloud\Query;
 use LeanCloud\CloudException;
@@ -122,6 +124,19 @@ public function testBecome() {
         $this->assertEquals($user2, User::getCurrentUser());
     }
 
+    public function testRefreshSessionToken() {
+        $user = new User();
+        $user->setUsername("alice4");
+        $user->setPassword("blabla");
+        $user->signUp();
+
+        $token = $user->getSessionToken();
+        $user->refreshSessionToken();
+        $this->assertNotEmpty($user->getSessionToken());
+        $this->assertNotEquals($token, $user->getSessionToken());
+        $user->destroy();
+    }
+
     public function testLogOut() {
         $user = User::logIn("alice", "blabla");
         $this->assertEquals($user, User::getCurrentUser());
@@ -191,6 +206,42 @@ public function testUnlinkService() {
         $user2->destroy();
     }
 
+    public function testGetRoles() {
+        $user = new User();
+        $user->setUsername("alice3");
+        $user->setPassword("blabla");
+        $user->signUp();
+
+        $role = new Role();
+        $role->setName("test_role");
+        $acl = new ACL();
+        $acl->setPublicWriteAccess(true);
+        $acl->setPublicReadAccess(true);
+
+        $role->setACL($acl);
+        $rel = $role->getUsers();
+        $rel->add($user);
+        $role->save();
+        $this->assertNotEmpty($role->getObjectId());
+
+        $roles = $user->getRoles();
+        $this->assertEquals("test_role", $roles[0]->getName());
+
+        $user->destroy();
+        $role->destroy();
+    }
+
+    public function testIsAuthenticated() {
+        $user = User::logIn("alice", "blabla");
+        $this->assertTrue($user->isAuthenticated());
+
+        $user->mergeAfterFetch(array("sessionToken" => "invalid-token"));
+        $this->assertFalse($user->isAuthenticated());
+
+        $user = new User();
+        $this->assertFalse($user->isAuthenticated());
+    }
+
     /*
      * Get current user with file attribute shall not
      * circularly invoke getCurrentUser.