没有需要PHP的结果

I have file structure like so:

root  
-folderA/file1  
--folderB/file2  
---folderC/file3  
----folderD/file4 

In file2, I use require('../file1') and it works fine. However, in file4, I use require('../../../file1') and there is no output.

I have checked the path to make sure file_exists and is_readable. I used:

try{ }catch(exception){ }

with no results.

I then copy-pasted my source code in file2 (knowing that it works) into file4, changing only the relative path. No output again.

Any help is appreciated. Thanks.