php中&&和｜｜的用法 这样用什么意思?

Question

$ckfid && $rs=$db->get_one("SELECT * FROM $table WHERE fid='$ckfid'");$rand=time().rand(0,9999);$url && $url = urlencode("$url&{$name}=");$rs[name] || $rs[name]="请选择...";