PHP Manual: posix

function posix_isatty(resource|int $file_descriptor): bool

Determines if the file descriptor file_descriptor refers to a valid terminal type device.

file_descriptor: The file descriptor, which is expected to be either a file resource or an int. An int will be assumed to be a file descriptor that can be passed directly to the underlying system call.

Returns true if file_descriptor is an open descriptor connected to a terminal and false otherwise.

Version	Description
8.5.0	Now raises an `E_WARNING` when an invalid `file_descriptor` is encountered.
8.4.0	Set errno (error number) to `EBADF` when the file descriptor/stream passed is invalid.
8.3.0	Type error `E_WARNING`s are now raised for integer coercions following the usual PHP type coercion semantics.

posix_isatty