diff --git a/dbjson.php b/dbjson.php
index 68a1380..c03884b 100644
--- a/dbjson.php
+++ b/dbjson.php
@@ -67,11 +67,12 @@ class dbjson
     */
   public function insertOne ($collection, $document)
   {
+    $uniqueKey = $this->uniqueKey ();
     $this->lockEX ();
     $this->db = $this->readDB ();
-    $this->db[$collection]["content"][] = array_merge (array (
-                                                   "_id"=>$this->uniqueKey ()),
-                                                 $document);
+    $this->db[$collection]["content"][$uniqueKey] = array_merge (
+                                                    array ("_id"=>$uniqueKey),
+                                                    $document);
     $this->writeDB  ($this->db);
     $this->lockUN ();
     return 1;
@@ -91,9 +92,10 @@ class dbjson
     $this->db = $this->readDB ();
     foreach ($documents as $document)
     {
-      $this->db[$collection]["content"][] = array_merge (array (
-                                                    "_id"=>$this->uniqueKey ()),
-                                                   $document);
+      $uniqueKey = $this->uniqueKey ();
+      $this->db[$collection]["content"][$uniqueKey] = array_merge (
+                                                      array ("_id"=>$uniqueKey),
+                                                      $document);
     }
     $this->writeDB  ($this->db);
     $this->db = null;
@@ -172,7 +174,22 @@ class dbjson
     {
       // Merge the new document with the old
       $tmp = $this->db[$collection]["content"][$key];
-      $tmp = array_merge ($tmp, $document);
+      // We need to merge the old and the new document.
+      // If there is an array in the document, it is overwrited
+      foreach ($document as $k=>$v)
+      {
+        if (is_array ($v))
+        {
+          if (isset ($tmp[$k]))
+            $tmp[$k] = array_merge ($tmp[$k], $v);
+          else
+            $tmp[$k] = $v;
+        }
+        else
+        {
+           $tmp[$k] = $v;
+        }
+      }
       $this->db[$collection]["content"][$key] = $tmp;
       // Remove the needed unset fields
       foreach ($unset as $field)
@@ -298,7 +315,8 @@ class dbjson
                 $fvals[1] !== "<" &&
                 $fvals[1] !== ">" &&
                 $fvals[1] !== "exists" &&
-                $fvals[1] !== "not exists")
+                $fvals[1] !== "not exists" &&
+                $fvals[1] !== "in_array")
               throw new \Exception ("Invalid filter operator provided", 500);
             if ($fvals[1] === "==" && $document[$fkey] === $fvals[0])
               $matchFilter = true;
@@ -316,6 +334,9 @@ class dbjson
             elseif (strtolower ($fvals[1]) === "not exists" &&
                     ! array_key_exists ($fkey, $document))
               $matchFilter = true;
+            elseif (strtolower ($fvals[1]) === "in_array" &&
+                    in_array ($fvals[0], $document[$fkey]))
+              $matchFilter = true;
             else
             {
               $matchFilter = false;