Description:
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The Direct IO functions are nice.

However, it is sometimes necessary to access file descriptors by their number.  For instance, a parent process can set up file descriptors 3, 4 and 5 for communication with the a child process (in addition to file descriptors 0, 1 and 2).  It would be nice if there were a way in PHP to get access to to file descriptor 3, so that PHP could interoperate with software that uses "extra" file descriptors.  (In particular, I am writing a mail filter.  The mail server sets up fd 3).

Getting access to the "extra" file descriptors is not possible at present, because the only way to get a file descriptor is to call dio_open on a file.  What if the file descriptor already exists?  There is currently no way to access it.

Perhaps a function such as dio_rawfd (int fdnum) could be added?  fdnum is an integer - the number of the file descriptor you want.  dio_rawfd returns a file descriptor resource for file descriptor number fdnum.