phpcms中index.php中这段代码有何意义？

if (strpos($_SERVER["REQUEST_URI"], "/CHA")===0 ) {
    $end = strpos($_SERVER["REQUEST_URI"], "/", 1);
    $channel = substr($_SERVER["REQUEST_URI"], 1, $end-1);
    $channelConfig = pc_base::load_config('channel');
    if ( !empty($channel) && isset($channelConfig[$channel]) ) {
        setcookie("channel", $channel, time()+7*86400, "/");
    }
}

phpcms中index.php里的这段代码我懂代码意思，但是不知道这样有何意义，是不是phpcms里面一般都这样？