安装metabox plugin 和活动：

/**** Add this code in your function.php ****/

$meta_boxes[] = array(
    \'id\' => \'post_sidebar\',         
    \'title\' => \'post Sidebar\',      
    \'pages\' => array(\'post\'),       
    \'priority\' => \'low\',            
    \'fields\' => array(          
            array(
                \'name\' => \'Post Sidebar\',               
                 \'id\' => \'post_sidebar\',        
                 \'type\' => \'select\',                            
                 "options" => array( "0" => "OFF", "1" => "Left side", "2" => "Right Side"),
            ),
        )
);
if ( class_exists( \'RW_Meta_Box\' ) )
{
    foreach ( $meta_boxes as $meta_box )
    {
        new RW_Meta_Box( $meta_box );
    }
}

/**** after single.php on get value using this one option ****/  

$sidebar_value = get_post_meta($post->ID,\'post_sidebar\',true);

if($sidebar_value == 1 && $sidebar_value!=0){
    // Add sidebar code for left side
}

if($sidebar_value==\'2\' && $sidebar_value!=0){
    // Add sidebar code for right side
}