How can I set a session variable?

Here is something I quickly wrote (not test yet)

Plugin: Sidebar Cookie
Hook Location: global_start

PHP Code:

PHP Code:

$show['sidebar'] = true;

if ($_REQUEST['do'] == 'hidesidebar')
{
   vbsetcookie('hidesidebar', 1, true);
}

$vbulletin->input->clean_gpc('c', 'hidesidebar', 'TYPE_INT');

if ($vbulletin->GPC['hidesidebar'] = 1)
{
    $show['sidebar'] = false;
} 


The template conditional would be:

<if condition="$show['sidebar']"> </if>

The button would point too:

?$session[sessionurl]do=hidesidebar