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).
注: 當安全模式開啟,PHP會檢查執行的腳本和 要操作的檔案或目錄是否有相同的UID(擁有者)