在站点地图中创建子网址

I'm trying to build a sitemap for my site. so far i was succeeded to build it.

Now i notice that i have some urls that related to other urls. which they are contain 90% of my site's urls.

For example i have this url:

www.mysite.com/mainurl

and those url which related to above url:

www.mysite.com/mainurl/mypage1
www.mysite.com/mainurl/mypage2
www.mysite.com/mainurl/mypage3

I was wondering if there is a way to related second urls to first url, something like sub url.

Also i have an other question, which type of url's format i should use?

This type: www.mysite.com/mainurl or this type: www.mysite.com/page.php?url=mypage1

Perhaps consider using PHP's explode function to split the url, then compare the values in a loop, something like:

$items = get_your_array();

foreach($items as $item)
{
    $urlParts = explode...
    foreach($urlParts as $part => $val)
    {
        // Organise parts into an associative array, so you can loop over it later
        // This would produce something that also could be accessed like...
        // $items['www.mysite.com']['mainurl']['mypage1'];
        // $items['www.mysite.com']['mainurl']['mypage2'];
        // Having the array key the same as the value as it would probably filter out duplicates, so you need to consider that
    }
}

As for your second questions, use the first style of URL's, they are better for SEO.