// Register BGMP Columns
function bgmp_columns_register( $bgmp_columns ) {
    $new_columns[ 'cb' ]        = "<input type=\"checkbox\" />";
    $new_columns[ 'title' ]     = _x( 'Title', 'column name' );
    $new_columns[ 'address' ]   = __( 'Address', 'bgmp' );
    $new_columns[ 'latitude' ]  = __( 'Latitude', 'bgmp' );
    $new_columns[ 'longitude' ] = __( 'Longitude', 'bgmp' );

    return $new_columns;
};
add_filter( 'manage_edit-bgmp_columns', 'bgmp_columns_register' );

// Display the column content
function bgmp_custom_columns( $bgmp_columns, $post_id ) {
    switch( $bgmp_columns ) {
        case 'address' :
            $address = get_post_meta( $post_id, 'bgmp_address', true );
            if ( $address ) {
                echo $address;
            } else {
                echo __( '<em>Not yet set</em>', 'bgmp' );
            }
        break;
        case 'latitude' :
            $address = get_post_meta( $post_id, 'bgmp_latitude', true );
            if ( $address ) {
                echo $address;
            } else {
                echo __( '<em>Not yet set</em>', 'bgmp' );
            }
        break;
        case 'longitude' :
            $address = get_post_meta( $post_id, 'bgmp_longitude', true );
            if ( $address ) {
                echo $address;
            } else {
                echo __( '<em>Not yet set</em>', 'bgmp' );
            }
        break;
    };
}
add_action( 'manage_bgmp_posts_custom_column', 'bgmp_custom_columns', 10, 2 );

// Register the column as sortable
function bgmp_sort( $columns ) {
    $custom = array(
        'address'   => 'address',
        'latitude'  => 'latitude',
        'longitude' => 'longitude'
    );
    return wp_parse_args($custom, $columns);
}
add_filter( 'manage_edit-bgmp_sortable_columns', 'bgmp_sort' );

function bgmp_columns_orderby( $vars ) {
    if ( isset( $vars['orderby'] ) && 'address' == $vars['orderby'] ) {
        $vars = array_merge( $vars, array(
            'meta_key' => 'bgmp_address',
            'orderby' => 'meta_value'
        ) );
    }
    if ( isset( $vars['orderby'] ) && 'latitude' == $vars['orderby'] ) {
        $vars = array_merge( $vars, array(
            'meta_key' => 'bgmp_latitude',
            'orderby' => 'meta_value_num'
        ) );
    }
    if ( isset( $vars['orderby'] ) && 'longitude' == $vars['orderby'] ) {
        $vars = array_merge( $vars, array(
            'meta_key' => 'bgmp_longitude',
            'orderby' => 'meta_value_num'
        ) );
    }
    return $vars;
}
add_filter( 'request', 'bgmp_columns_orderby' );