Function set_value() not working as expected

[eluser]ifew[/eluser]
ok, this patch can use for

<input type='text' name="optoin[0]" size="30" value="<?=set_value('optoin[0]'); ?>"/>
<input type='text' name="optoin[1]" size="30" value="<?=set_value('optoin[1]'); ?>"/>
<input type='text' name="optoin[2]" size="30" value="<?=set_value('optoin[2]'); ?>"/>

and set in rule

array(
'field' => 'skill_input[0]',
'label' => 'lang:user_option',
'rules' => 'trim|htmlspecialchars|xss_clean'
),
array(
'field' => 'skill_input[1]',
'label' => 'lang:user_option',
'rules' => 'trim|htmlspecialchars|xss_clean'
),
array(
'field' => 'skill_input[2]',
'label' => 'lang:user_option',
'rules' => 'trim|htmlspecialchars|xss_clean'
)