function editarProducto()
{
    $id = $this->input->post('productoID');;
    $this->db->where('id', $id);
    $query = $this->db->get('items');
    return $query->result();
}

...<form id="SelectProd-form" method="post">
                                <select id="productoID" name="productoID" class="form-control">
                                    <option value="">Seleccionar</option>
                                    <?php
                                    foreach ($editarID as $key => $value) {
                                        echo "<option value='".$value->id."'>".$value->nombre."</option>";
                                    }
                                    ?>
                                </select>
                            </div>
                            <br>
                            <button id="botonSelectProd" type="submit" class="form-group" name="submit">Seleccionar</button>
                            </form>
                        </div>
                    </div>
                    <div id="editarProducto">
                    <form id="editarProducto-form" action="<?php echo site_url('admin/editarProducto'); ?>" method="post">
                        <div id="msjRegistro" class="login-form-main-message"><?php echo validation_errors(); ?></div>
                        <div class="form-group">
                            <label for="nombre" class="cols-sm-2 control-label">Nombre</label>
                            <div class="cols-sm-10">
                                <div class="input-group">
                                    <span class="input-group-addon"><i class="fa fa-forward fa" aria-hidden="true"></i></span>
                                    <input type="text" class="form-control" name="nombre" placeholder="Ingresa el nombre del producto" value="<?php echo set_value('nombre'); ?>" />
                                </div>
                            </div>
                        </div>
                        <div class="form-group">
                            <label for="precio" class="cols-sm-2 control-label">Precio</label>
                            <div class="cols-sm-10">
                                <div class="input-group">
                                    <span class="input-group-addon"><i class="fa fa-dollar fa" aria-hidden="true"></i></span>
                                    <input type="number" min="0.00" max="100000.00" step="0.01" placeholder="Ingresa el precio en pesos" class="form-control" name="precio" value="<?php echo set_value('precio'); ?>"/>
                                </div>
                            </div>
                        </div>...