php - 在db的下拉选择器上设置默认值

I have a dropdown menu on my view that lets me select different items from the table. But, since by default there is one possible option at this instance, I want to set it instead of manually changing each one.

This is the code:

<td><?php   
        $tabindex = 1;          
        $extras = 'class = "smallInput" tabindex='.$tabindex;
        $tracking_status_array = array ();
        $tracking_status_array += array ('' => 'Select Status' );
        foreach ( $tracking_status_list as $status ) {
          $tracking_status_array += array (trim ( $status->tracking_status_id ) =>  trim ( $status->status_text )  );
        }
        echo form_dropdown ( 'tracking_status_id[]', $tracking_status_array, set_value ( 'tracking_status_id[]'), $extras);
        ?></td>

I dont want to remove the rest of the values because maybe in the future i might need one of those others, i only want to set one as default instead of blank as default