What is "clear session"?

[Admin]

Add this action to member.php:

// ############################### start clear sessions ###############################
if ($action=="clears") {
  include("./global.php");
  if ($bbuserinfo[userid]!=0 and $bbuserinfo[userid]!=-1) {
    $DB_site->query("UPDATE user SET lastactivity='".(time()-$cookietimeout)."',lastvisit='".time()."' WHERE userid='$bbuserinfo[userid]'");
  }
  $DB_site->query("DELETE FROM session WHERE sessionhash='".addslashes($session[dbsessionhash])."'");
  $DB_site->query("DELETE FROM session WHERE userid='$bbuserinfo[userid]'");
  eval("standarderror(\"".gettemplate("error_sessionclear")."\");");
}

and link to member.php?s=$session[sessionhash]&action=clears
Add a template named error_sessionclear and put your message there.