Remove this:
// Administration: Teach wordpress to make the column sortable
function anco_project_year_column_orderby( $vars ) {
if ( isset( $vars['orderby'] ) && 'anco_project_year_from' == $vars['orderby'] ) {
$vars = array_merge( $vars, array(
'meta_key' => 'anco_project_year_from',
'orderby' => 'meta_value_num'
) );
} else if ( isset( $vars['orderby'] ) && 'anco_project_year_to' == $vars['orderby'] ) {
$vars = array_merge( $vars, array(
'meta_key' => 'anco_project_year_to',
'orderby' => 'meta_value_num'
) );
}
return $vars;
}
add_filter( 'request', 'anco_project_year_column_orderby' );
and add this:
add_action( 'pre_get_posts', 'my_slice_orderby' );
function my_slice_orderby( $query ) {
if( ! is_admin() )
return;
$orderby = $query->get( 'orderby');
if( 'anco_project_year_from' == $orderby ) {
$query->set('meta_key','anco_project_year_from');
$query->set('orderby','meta_value_num');
} elseif('anco_project_year_to' == $orderby) {
$query->set('meta_key','anco_project_year_to');
$query->set('orderby','meta_value_num');
}
}