(PHP 4, PHP 5, PHP 7)
posix_mkfifo — Create a fifo special file (a named pipe)
$pathname
   , int $mode
   ) : bool
   posix_mkfifo() creates a special
   FIFO file which exists in the file system and acts as
   a bidirectional communication endpoint for processes.
  
pathname
       Path to the FIFO file.
      
mode
       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).
      
   成功时返回 TRUE, 或者在失败时返回 FALSE。
  
Note: 当启用 安全模式时, PHP 会检查被操作的文件或目录是否与被执行的脚本有相同的 UID(所有者)。