Look into non-console I/O

[clue]

• Process pipes
• Remote telnet console
• etc.

[clue]

posix_isatty() may help here. See also http://stackoverflow.com/questions/11327367/detect-if-a-php-script-is-being-run-interactively-or-not

This could also affect MS Windows support (#18).

# pipe input
echo input | php example.php

# pipe interactive input
cat | php example.php

# pipe output
php example.php | cat

# closed input pipe
php example.php 0<&-

[clue]

For the reference: The last example has actually lead to discovering a bug in PHP:

# bugged: closed input pipe
php example.php 0<&-

# instead: null input pipe
php example.php </dev/null

See also reactphp/stream#81 and the upstream bug report https://bugs.php.net/bug.php?id=74252.