posix_mkfifo() creates a special FIFO file which exists in the file system and acts as a bidirectional communication endpoint for processes.
The second parameter mode has to be given in octal notation (e.g. 0644). The permission of the newly created FIFO also depends on the setting of the current umask(). The permissions of the created file are (mode & ~umask).
참고: 안전 모드를 활성화했을 경우, PHP는 작업하려는 디렉토리가 실행중인 스크립트와 같은 UID(owner)를 가지고 있는지 확인합니다.