By cj on Feb 12, 2013
The PHP RFC process has been in place for a while, and users new to core PHP development are starting to use RFCs to propose desirable features.
Here are some personal observations and suggestions that show how I have seen feature acceptance and the RFC process work in practice. These notes augment the steps in How To Create an RFC. I hope they help set expectations about the PHP RFC process and feature acceptance in the PHP language.
Before starting an RFC, review existing RFCs and search the mail list archives for similar ideas. Use this information to explain what your RFC will bring to the language.
If you're new to PHP core development, mail the "internals" mail list to judge interest before you start your RFC. If you get no reaction (this is likely) or positive reaction then create the RFC. Core PHP developers with karma will know when they can skip this step.
Avoid presenting an RFC idea to the "internals" mail list with email that begins "I don't know much about ... but ...". Do some research first.
There are many really good ideas for improving PHP, however some of them are really tedious or technically risky or hard. If you are about to email the "internals" mail list saying "someone should do ...", then don't hit "Send". Work out how you could do it, and then send a patch.
If the overall goals of PHP are not clear to you, you may not be alone. However, as an RFC writer you need to learn the general trajectory of the language and where web development is heading. You then need to enthuse everyone with your feature and show what it brings to the language.
Don't start an RFC (or mail list discussion) about standardizing PHP function names and function argument orders. There are several historical reasons why the functions are what they are (including compatibility with underlying libraries), and many good reasons why the change would be counter-productive causing more end-user confusion, would lead to unmaintainable PHP engine code, and generally be a waste of everyone's time when they could be doing more interesting projects. This has been discussed ad infinitum. Review previous discussions and feel free to fork PHP on github.
Your RFC should talk about all PHP areas that will be affected: php.ini, different SAPIs, engine, extensions, etc. List similar features. List similar features in other languages. Link to references. Give an estimate of the actual positive impact to user code. Put the proposed voting options in the RFC so they can be included in its discussion. Include the proposed acceptance criteria (2/3 or 50%+1 majority - see the original Voting RFC) to avoid later argument.
Your RFC will be used to create the PHP documentation, so make its sections re-usable. Explain concepts and details. Keep the RFC technical and have plenty of examples.
Many current PHP RFCs don't contain enough detail, nor do they capture the pros & cons that were discussed on the mail list. You can, and should, do better than these RFCs.
An implementation is not mandatory while proposing an RFC but it can help persuade people and help fine-tune the design. Note that if you are unable to implement the RFC, and no one else volunteers during the discussion period, then your RFC is unlikely ever to be implemented.
Don't start an implementation too early. Get support for the feature concept from the "internals" mail list before spending time on coding - unless you want a learning experience.
If you do have an implementation, make it clear whether the implementation is a simple prototype or is expected to be the final code. This is specially important during the vote.
It's easy to get sidetracked by mail list trolling or well intentioned but over-eager discussion. Take advice on board but make sure your feature doesn't end up being designed by a committee. Don't blame the "PHP core community" for derailing discussions when the issues of non- code-contributors on the mail list are at fault.
For every user who wants a backwardly incompatible change to PHP, there is a user who will scream that this will be disastrous to them. As the RFC writer you need to walk the line between these groups. At voting time, other people may see the line in a different place than you do.
There is no need to respond to every discussion email individually. You should batch up your responses and manage the discussion intelligently.
Don't get side tracked by how long it will take a feature to reach end users. It will reach them eventually. You can always supply an unofficial patch or maybe create a PECL extension for users of current versions of PHP.
Don't let mail list discussion drag on too long. High levels of discussion can be a symptom that an RFC is contentious. Having an early vote about only the feature's concept can prevent over-investment in an RFC and implementation.
With long, fragmented discussions, not everyone will read every email. Update the RFC at regular intervals, and let people know what has changed. Include the RFC URL in all your emails so anyone dipping into a mail thread has a better chance of finding the RFC.
PHP is popular so you can often find support from "many" people for cool language features. This doesn't mean those features are a "good thing" for the language or its implementation.
There are multiple PHP communities. Don't interpret support in one community as universal support. Listen carefully to the key PHP developers on the "internals" mail list (they may not be the ones doing the most discussion). They are the people who will undoubtedly end up doing final integration of the feature (e.g. with the op-code cache), fixing edge cases, and maintaining it in the long term. They are the ones that have seen the PHP code base complexity grow and become more difficult to maintain and extend. Even if they like your idea, they may not be able to contribute time and effort to make it stable.
The PHP core development community needs more end-users to become core language developers but the barrier to entry is high because of the complexity of the API, and because new features need very careful integration with a complex language. See the point above about existing developers not having enough time to support every good idea. This just means you need perseverance to become a core developer yourself. You can gain karma by being a regular code contributor before starting your magnum opus RFC.
Some areas of PHP are complex or niche. Sometimes feature suggestions will be greeted by an apparent lack of interest. Don't be discouraged. This just means you need to take a stronger leadership role, and also prove your credentials by first working on the existing code base.
Keep your RFC updated with a summary of all the positive and negative mail list discussion points and examples.
- This prevents arguments being rehashed on the mail list each year.
- Documentation will have clear use cases and show what does and doesn't work.
- Future RFC writers can see trends and build on previous ideas.
Before initiating a vote on your RFC, make sure the RFC contains enough detail so that the vote is solely on the RFC contents, not on any half-remembered or misinterpretable mail list discussions. Un- (or badly) expressed intentions will only cause you frustration when your RFC is rejected.
Don't leave any ambiguity in the RFC. As well as stating what will be changed, also state what won't be changed. Ambiguity will hurt the chances of a successful outcome because voters will be unsure that the feature has been fully thought through. Make sure there are no "Open Issues" in the RFC when voting. Make a decision about the choices before opening the vote, or mark the issues clearly as "Future topics for exploration".
Make sure any vote is clear about what is being voted on: is it the idea, the specification, or the implementation? Is a particular version of PHP being targeted? Is the implementation going to be merged to the core language or made as a PECL extension?
Warn the "internals" mail list before starting the vote. This notification gives you a chance to fine tune the wording of your poll; this wording has caused contention in the past. The approaching deadline may also cause last-minute RFC responses. These may be significant enough to require further discussion.
Set a deadline for the vote (sadly the current voting RFC doesn't require this). Having a deadline will forestall suggestions that a vote was deliberately left open until it succeeded, and then closed before the "negative" side could rally support.
During the voting period, it is common for people to continue mail list discussion. You may need to halt the vote and address any issues.
Prior to the end of the voting period, remind the mail list that the vote is about to close.
Positive voting poll outcomes for RFs that are just "concepts" can be interpreted as support for "good ideas" rather than being a definitive guarantee that a feature will appear in a future version of PHP. As a feature is later investigated and further discussed, the early vote may become irrelevant. Similarly, where there is no chance of an implementation being written, a positive poll outcome is just an indicator of desire.
If your RFC is rejected, it is not the end of the world. Sometimes ideas are submitted "before their time", and it takes an acclimatization period for other developers to see their value. As the core PHP developer base goes through natural turn-over, revisiting an idea after a (long) period may result in different appreciation. (This does not apply to some ideas, for example standardizing function names). See the previous points about becoming a core contributor - having karma goes a long way towards getting an RFC accepted, not only because experienced contributors know which RFCs are worth suggesting, and know how to make proposals understandable. When your RFC is rejected, continue working with the PHP core development community and revisit the RFC later.
You can always fork PHP from github.
In summary, the PHP development process is an organic process and subject to flexibility. It is based heavily around users contributing features that they require. This therefore requires high investment from users who want change. Very rarely do PHP core developers have bandwidth to take on external ideas, no matter how good they are. Feature acceptance has to be pragmatic. The core PHP contributors would love to see more people get commit karma and contribute to PHP.
This post has gone on long enough. My notes are current for the time being. I'm sure there are observations or clarifications you can make. If you want to add anything, please post a comment.
(Note: this page has been augmented and re-ordered since first being published)