jquery 给下拉框赋值

jquery代码

$('.edit-modal').on('click',function(){
        var id = $(this).attr('href');
        var value = $(this).attr('value');
        // get data
        var url="<?php echo $root;?>/editRobotActionNum";
        $.ajax({
            url: url,
            data: 'id='+value,
            type : 'POST',
            dataType : 'json',
            success : function(json)
            {
                $('#editId').attr('value',json.id);
                $('select#edit_material_id').val(json.material_id);
                $('select#edit_station_id').val(json.station_id);
                $('#edit_up_action').attr('value',json.up_action);
                $('#edit_turn_action').attr('value',json.turn_action);
                $('#edit_down_action').attr('value',json.down_action);
                
            }
        });

        $(id).modal('show');
    });

html

<select class="form-control" id="edit_material_id" name="material_id">
    <option value=""></option>
    <?php foreach($stock_info as $row):?>
        <option value="<?php echo $row['id'];?>"><?php echo $row['name'];?>    </option>
    <?php endforeach;
</select>