form_open操作URL错误

have this code

<?php echo form_open('controller/method'); ?>

and it supposed to create this code

<form accept-charset="utf-8" method="post" action="http://localhost/codeigniter/controller/method">

but it created

<form accept-charset="utf-8" method="post" action="http://localhost/codeigniter/?controller/method">

There is an extra ”?” before the controller name.

How can fix that problem ? Thanks in advance

This can happen if you set enable_query_strings to TRUE

$config['enable_query_strings'] = FALSE;