This function returns False (output is being redirected) regardless of the form of redirection. On Windows, both of these are redirected:
- php.exe script.php > outFle.txt
- php.exe script.php | Tee outFle.txt
In the second case, Tee causes the redirection to also echo to the console.
An edge usage is: in debugging a long-running script, output is wanted both in a file for later review and also in the console so it's visible in real time. But if the script alters its output based on this function, then in the second case it will produce output as if for redirection only, even though Tee enables console output.