Fatal error: Call to a member function getTableColumns() on a non-object in /hosting/www/mydomain/libraries/joomla/table/table.php on line 188

class MtrainingCkTableGroup extends MtrainingClassTable
{
	/**
	* Constructor
	*
	* @access	public
	* @param	object	&$db	Database connector object
	* @param	string	$tbl	Table name
	* @param	string	$key	Primary key
	* @return	void
	*/
	public function __construct(&$db, $tbl = '#__training_groups', $key = 'id')
	{
		parent::__construct($tbl, $key, $db);
	}


}

class MtrainingTableGroup extends MtrainingCkTableGroup
{
	/**
	* Constructor
	*
	* @access	public
	* @param	object	&$db	Database connector object
	* @param	string	$tbl	Table name
	* @param	string	$key	Primary key
	* @return	void
	*/
	public function __construct(&$db, $tbl = '#__training_groups', $key = 'id')
	{
		parent::__construct($tbl, $key, $db);
	}

}

class MtrainingTableGroup extends MtrainingCkTableGroup
{
	/**
	* Constructor
	*/
	public function __construct(&$db, $tbl = '#__training_groups', $key = 'id')
	{
		parent::__construct($db, $tbl, $key);  //HERE declaration should be the same
	}

}

class MtrainingTableGroup extends MtrainingCkTableGroup
{
	/**
	* Constructor
	*/
	public function __construct(&$db, $tbl = '#__training_groups', $key = 'id')
	{
		parent::parent::__construct($tbl, $key, $db);  //HERE call to the parent of original
	}

}