Python (sympy) string to php issues

Python (sympy) string to php issues

I have a weird situation. I am calling a python program from my webpage
(written in PHP). It normally works fine, but I when I add
import sympy
I get problems (this is one line is the only difference).
Basically, when I run the program from the terminal (with 'import sympy')
it works just fine (prints 6 strings), but when I call the program from my
php file it returns an empty array (instead of an array with 6 strings
like it should). The two commands are
terminal:
python MyProgram.py arg1
from php:
$command='python MyProgram.py arg1';
exec($command, $output);
Any ideas? Thanks in advance!