Get the value from DropDown list [RESOLVED]

Absolutely.

In your controller:

PHP Code:

$milestone_id = $this->input->post('milestone_id');
$this->db
->select('SUM(estimated_hours) as value_sum')
->from('project_has_tasks')
->where('milestone_id', $milestone_id);
$sum = $this->db->get()->row()->value_sum;