File access fails in external lib called from extension

I have an external library (C++, .so shared lib) that uses
<fcntl.h> functions (open, etc) to access local disk resources,
to create a data repository.

I have written a standalone KDE client that affirms that the
library is functioning correctly.

When I try to use a class from that library in a PHP-C++ extension
however, the class is usable, but the file io fails.

Is this a permissioning issue? (Apache/Php not allowing calls to
disk access?) Or am I missing something?

Should a C/C++ extension still be able to access system/file IO?

Cheers,

Andrew