diff --git a/api/blueweather.php b/api/blueweather.php
index 86b64ca..12a1580 100644
--- a/api/blueweather.php
+++ b/api/blueweather.php
@@ -42,6 +42,9 @@ class BlueWeather
 
     }
 
+    // -------------------
+    // - user management -
+    // -------------------
 
     /**
      * Function to login users
@@ -85,6 +88,30 @@ class BlueWeather
         return $token_hash;
     }
 
+    /**
+     * Function to check if a session token exists and get the corresponding user
+     *
+     * @param string $session session token
+     *
+     * @return int (-1: does not exist; x>0: userId)
+     */
+    public function checkSession($session)
+    {
+        $sql = "SELECT * FROM `sessions`
+        WHERE`session`=\"".$this->_con->real_escape_string($session)."\"";
+        $result = $this->_con->query($sql);
+
+        if (!$result->num_rows > 0) {
+            return -1;
+        }
+
+        // only one row will be returned
+        $data = $result->fetch_assoc();
+
+        return($data['userId']);
+    }
+
+
     // --------------------
     // - getter functions -
     // --------------------
@@ -182,7 +209,7 @@ class BlueWeather
             }
         }
     
-        if (isset($maxVals) && $maxVals > 0 && count($measvalues) > $maxVals) {
+        if (isset($maxVals) && $maxVals > 0) {
             // build the new measvalues array with respect to maxVals for each sensor
     
             $finalMeasvals = array();
@@ -198,6 +225,10 @@ class BlueWeather
                         array_push($rawMeasvalsOfThisSensor, $measvalue);
                     }
                 }
+
+                if (count($rawMeasvalsOfThisSensor) <= $maxVals) {
+                    continue;
+                }
     
                 // always sum up the same amount of values to get a new array
                 // which doesn't have more than $maxVals values
diff --git a/api/json.php b/api/json.php
index da76b21..2216c04 100644
--- a/api/json.php
+++ b/api/json.php
@@ -7,7 +7,8 @@
  *
  * @param locId
  * @param range   (range[from]: from UNIX time; range[to]: to UNIX time)
- * @param maxVals (maximum measvals to be transmitted; if more are present in the timespan, the avarage will be calculated)
+ * @param maxVals (maximum measvals to be transmitted; if more are present 
+ *                in the timespan, the avarage will be calculated)
  *
  * @category Tools
  * @package  BlueWeather
@@ -26,7 +27,9 @@ $blueweather = new BlueWeather($config);
 
 if (isset($_GET['locId'])) {
     // get data of given location
-    $data = $blueweather->getLocationData($_GET['locId'], $_GET['range'], $_GET['maxVals']);
+    $data = $blueweather->getLocationData(
+        $_GET['locId'], $_GET['range'], $_GET['maxVals']
+    );
 } else {
     $data = $blueweather->getAllLocations();
 }