There are 3 Methods in form creation

1.)<?php echo form_open('welcome/index'); ?>
This will create a simple form

 2.)<?php echo form_open_multipart('welcome/index'); ?>
This is used to handle file upload possibilities.

 3.)<?  $attributes = array('id' => 'myform');

echo form_open('email/send', $attributes); ?>

 We  can set attributes for the form in its parameter itself.