CONTOH EDIT COMBOBOX (CI Framework)

HTML
echo form_dropdown("subktgr",$subktgr,"",'id="id_subktgr" class="form-control"');

JQUERY/AJAX
function edit(id)
{
	$('#form')[0].reset();
    $.ajax({
	    url : "<?php echo site_url('ktgr_brng/ajax_edit/')?>/" + id,
	    type: "GET",
	    dataType: "JSON",
	    success: function(data)
	    {
	    	method = 'ubah';
			url = '<?php echo site_url('ktgr_brng/proses_edit')?>';
	        $('[name="id_ktgr_brng"]').val(data.id_ktgr_brng);
	        $('[name="ktgr_brng"]').val(data.ktgr_brng).attr("readonly","readonly");
	        $('[name="subktgr"]').val(data.sub).change();
	        $('[name="keterangan"]').text(data.keterangan);
			$('#form-modal').modal('show');
	        $('.modal-title').text('Form Edit Data');
	        tampil_itemasset();
	    },
	    error: function (jqXHR, textStatus, errorThrown)
	    {
	        alert('Error get data from ajax');
	    }
	});
}

PHP (LOGIC)
function ajax_edit($id)
{
   $data = $this->m_all->get_by_id($this->table, $this->primary, $id);
   echo json_encode($data);
}

PHP (QUERY)
function get_by_id($table, $id_table, $id)
{
	$this->db->select('*');
    $this->db->from($table);
    $this->db->where($id_table, $id);
    $q = $this->db->get();
    return $q->row();
 }

DESIGN TABLE (Dalam konteks kasus ini/contoh)
id_ktgr_brng	ktgr_brng	sub	keterangan
1	            Jas hujan	0	Kategori jas hujan
2	            lampu	    0	kategori lampu