Get the value from DropDown list [RESOLVED]

hi there,

is there any possible to get the value (on live) from this:

Code:

<div class="form-group">
        <label for="milestone_id"><?=$this->lang->line('application_milestone');?></label>
        <?php   $milestones = array();
                $milestones['0'] = '-';
                 foreach ($project->project_has_milestones as $milestone):
                    $milestones[$milestone->id] = $milestone->name;
                endforeach;
        if(isset($task)){$milestone_selected = $task->milestone_id;}else{$milestone_selected = "";}
        echo form_dropdown('milestone_id', $milestones, $milestone_selected, 'style="width:100%" class="chosen-select"');?>
</div>

To this?

Code:

$result = mysql_query('SELECT SUM(estimated_hours) AS value_sum FROM project_has_tasks WHERE milestone_id ="???????????????"');
$row = mysql_fetch_assoc($result);
$sum = $row['value_sum'];