php man page for posix_isatty

POSIX_ISATTY(3) 							 1							   POSIX_ISATTY(3)

posix_isatty - Determine if a file descriptor is an interactive terminal

SYNOPSIS
       bool posix_isatty (mixed  $fd)

DESCRIPTION
	Determines if the file descriptor $fd refers to a valid terminal type device.

PARAMETERS
	      o $fd
		-  The	file  descriptor,  which  is  expected to be either a file resource or an integer. An integer will be assumed to be a file
		descriptor that can be passed directly to the underlying system call.  In almost all cases,  you  will	want  to  provide  a  file
		resource.

RETURN VALUES
	Returns TRUE if $fd is an open descriptor connected to a terminal and FALSE otherwise.

SEE ALSO
       posix_ttyname(3).

PHP Documentation Group 													   POSIX_ISATTY(3)