如何阻止更改URL并查看其他用户文件夹的功能

I have a directory of folders and I want to prevent the user named "x" whos files are availiable like this:reports/x/2015/04/ from changing the x to y and seeing all of those folers in y. I have the sessions working so that you need to be logged in to see any folders, but if you are logged in as x you can see the y folder by changing the URL. here is my index.php.I have a directory of folders and I want to pre