How can this problem be solved?

The path is annoying. This code file is in & nbsp;/admin/& nbsp; the file name is. php $ B = aa; $ a = '.. /'. $ B; mkdir ($ a, 0700); the generated path is the previous layer. It should be & nbsp;/aa/to generate such a directory. Domain name access & nbsp; http: // a path is annoying.
This code file is named a. php under/admin /.

$ B = aa;
$ A = '../'. $ B;
Mkdir ($ a, 0700 );

The generated path is the previous layer. It should be/aa/to generate such a directory. Domain name access: http://a.com/aa/

The previous layer cannot be obtained. Share:
------ Solution --------------------
Mkdir ($ a, 0666 );

Check whether the directory has been generated
Since aa does not have files, it is impossible to access them.
------ Solution --------------------
$ B = aa; it should be $ B = 'a ';