Added a function to disconnect from mysql server

MysqliDb.php

@@ -289,6 +289,20 @@ class MysqliDb
         }
     }
 
+    /**
+     * A method to disconnect from the database
+     *
+     * @throws Exception
+     * @return void
+     */
+    public function disconnect()
+    {
+        if (!$this->_mysqli)
+            return;
+        $this->_mysqli->close();
+        $this->_mysqli = null;
+    }
+
     /**
      * A method to get mysqli object or create it in case needed
      * 

readme.md

@@ -699,6 +699,11 @@ if($db->has("users")) {
 }
 ``` 
 ### Helper methods
+Disconnect from the database:
+```php
+    $db->disconnect();
+```
+
 Reconnect in case mysql connection died:
 ```php
 if (!$db->ping())