public function add_fields( $fields )
	{
		if ( !is_array( $fields ) )
		{
			$fields = array( $fields );
		}
		
		// merge the new values with the existing ones.
		$this->fields = array_merge( $this->fields, $fields ); 
	
		// return self so we can continue running the next function
		return $this;
	}