$href = "http://www.site.org/index.php?do=/profile-2/photo/";

preg_match('~http://www\.site\.org/index\.php\?do=/profile-2/([^/]+)/~', $href, $m);
var_dump($m);

$href = "http://www.site.org/index.php?do=/profile-2/photo/";

var_dump(explode('/', $href));

$href = "http://www.site.org/index.php?do=/profile-2/photo/";

var_dump($query = parse_url($href, PHP_URL_QUERY));
parse_str($query, $q);
var_dump($q);