Try
// 1. Register the column
add_filter( 'manage_edit-post_columns', 'price_column_register' );
function price_column_register( $columns ) {
$columns['price'] = __( 'Price', 'theme' );
return $columns;
}
// 2. Display the column content
add_action( 'manage_posts_custom_column', 'price_column_display', 10, 2 );
function price_column_display( $column_name, $post_id ) {
if ( 'price' != $column_name )
return;
$price = get_post_meta($post_id, 'price', true);
if ( !$price )
$price = '<em>' . __( 'undefined', 'theme' ) . '</em>';
echo $price;
}
// 3. Register the column as sortable
add_filter( 'manage_edit-post_sortable_columns', 'price_column_register_sortable' );
function price_column_register_sortable( $columns ) {
$columns['price'] = 'price';
return $columns;
}
// 4. here is the sorting brain
add_filter( 'request', 'price_column_orderby' );
function price_column_orderby( $vars ) {
if ( isset( $vars['orderby'] ) && 'price' == $vars['orderby'] ) {
$vars = array_merge( $vars, array(
'meta_key' => 'price',
'orderby' => 'meta_value_num',
'order' => 'asc'
) );
}
return $vars;
}