PHP RFC: Add file_descriptor() function


When dealing with I/O in PHP, one deals with streams as an abstraction over the file system. This abstraction is convenient in giving a uniform interface without needing to deal with the underlying system. However, sometimes one needs to deal with the file system directly via the file descriptor, for example when interacting with a USB device.

PHP supports retrieving the file descriptor of a stream within the engine, but does not expose this capability to userland. However, with the magic of FFI it is possible to expose the underlying file descriptor of a stream if it exists, by stubbing out the Zend engine.

This RFC address this issue by proposing the addition of a native file_descriptor() function.


The proposal is to add the following function to PHP:

/** @param resource $stream */
function file_descriptor($stream): int {}

Which returns the underlying file descriptor of a stream if it exists, or throws a TypeError if the resource is not a stream or does not have an underlying file descriptor.

Backward Incompatible Changes

This RFC does not contain any backwards incompatible changes.

Proposed PHP Version

Next minor version, i.e. PHP 8.3.

Proposed Voting Choices

As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.

Voting started on 2023-XX-XX and will end on 2023-XX-XX.

Accept Add file_descriptor function RFC?
Real name Yes No
Final result: 0 0
This poll has been closed.


GitHub pull request: https://github.com/php/php-src/pull/10342

After the project is implemented, this section should contain

  • the version(s) it was merged into
  • a link to the git commit(s)
  • a link to the PHP manual entry for the feature


FFI implementation: https://github.com/ppelisset/php-fileno
AFUP Forum PHP Talk (in French) describing the use case: FFI : De nouveaux horizons pour PHP - Pierre PELISSET - Forum PHP 2022

rfc/file-descriptor-function.txt · Last modified: 2023/01/16 14:58 by girgias