Commands working fine in putty but not using exec() in PHP - php

Question

So I have installed shhavel's facerec (https://github.com/shhavel/facerec) on my VPS (Ubuntu 14.04.5) and it works perfectly fine when I use it from within putty:
facerec list
jenniferlawrence
emmawatson
However, from within PHP when using the exec() function, the only command that works is facerec -help, all other commands produce an error similar to the following:
facerec list 2>&1
Traceback (most recent call last):
File "/usr/local/bin/facerec", line 359, in
sys.exit(__main__())
File "/usr/local/bin/facerec", line 356, in __main__
return args.func(args)
File "/usr/local/bin/facerec", line 159, in list
for subject in os.listdir(subjects_directory):
OSError: [Errno 2] No such file or directory: './subjects'
The PHP script:
exec('facerec list 2>&1', $output);
foreach($output as $string) {
echo $string."<br>";
}
How do I approach fixing this problem?

Answer 1

Found the problem:
The "subjects"-folder was located in /root/ which the PHP script did not have the permission to access
Possible solutions:
change open_basedir in PHP settings to none (See here: open_basedir restriction in effect. File(/) is not within the allowed path(s):)
install shhavel/facerec as the right user (not as root)
move the subjects-folder to a different location and change the facerec python script accordingly