PHP and P++

PHP has been around for a long time; a previous version of the LWN site was implemented in PHP/FI in 1998. For most of its 25 years of existence, PHP has been criticized from multiple directions. Its development community has done a lot of work to address many of those criticisms while resisting others that, it was felt, went against the values of the language. Often these changes have forced code written in PHP to change as well; such changes tend to be the most controversial.

For example, consider the current controversy over "short open tags". PHP code is embedded within an HTML page with a sequence like this:

    <?php /* PHP code */ ?>

Back in the early days, though, the language also understood an abbreviated version:

    <? /* PHP code */ ?>

The latter form is, among other things, not properly XML compliant and has been deprecated for years. If the short_open_tag setting is enabled, though, these tags will still be recognized. The PHP community decided some time ago that it wanted to remove all settings that affect the language globally, and it seems that short_open_tag is the only one remaining. But a proposal to remove it has been through multiple iterations, has elicited strong opposition, and has inspired lengthy discussion threads on the project's mailing lists. The PHP project resolves such issues through voting; as of this writing, there are 28 votes in favor of removal and 24 opposed. Unless things change before the vote closes on August 20, this particular measure will fail to reach the 2/3 majority required to pass.

Bringing peace

This vote highlights the sort of division that can be found in the PHP community. Referring to "a growing sense of polarization", PHP developer Zeev Suraski tried to improve the situation with a proposal titled "Bringing Peace to the Galaxy"; so far, it would appear to have failed to do so, at least in the way that was intended.

Suraski described the disagreement as being between those who want to push the language forward and those who value backward compatibility above almost all else. "To a large degree, these views are diametrically opposed. This made many internals@ discussions turn into literally zero sum games - where when one side 'wins', the other side 'loses'". The answer that he came up with was to give both sides what they want by splitting the language in two:

• "Classic" PHP would continue to be developed with a strong emphasis on keeping millions of lines of existing code working. The language would not be frozen, but it would be highly resistant to changes that break compatibility.
• A new language, called "P++" for now, would take the opposite approach, breaking compatibility and adding features (such as strict typing, greater consistency across the language, new types and, naturally, killing off short open tags).

On its surface, this looks like a fork of PHP or, at a minimum, a split like that seen between Python versions 2 and 3. Suraski envisions something a bit different, though. Unlike Python, the PHP community would continue to develop (and add features to) its old version, with no plans for leaving it behind at some point. He also envisions supporting both languages from the same code base and a common runtime system. A single binary would implement both PHP and P++. So, rather than creating a fork, Suraski aims to create a single project with two faces.

Suraski's post (along with the subsequently posted P++ FAQ) was intended to provoke discussion; as one might imagine, it succeeded. Some developers like the idea, but many more seem to be concerned about it, for a number of reasons. One of those was expressed by Dan Ackroyd among others:

Suraski optimistically responded that his proposal "will take no additional resources", mostly as the result of the use of a single code base. It is not clear that others in the community find this argument persuasive, though.

The idea of "rebranding" PHP with the new language is appealing to Suraski, who sees it as a way of getting away from PHP's not-entirely-positive reputation. Others, such as Nikita Popov, worried that rebranding will leave a valuable name behind without any corresponding benefit. Rebranding is also something that can only be done once, Popov said; it won't be an option five years down the road when the desire to add yet another set of incompatible features arises. Suraski responded that rebranding can bring new life to a project by attracting interest and getting developers who have written PHP off to take another look. The backward-compatibility break in P++ was described as a one-time thing, where all of the changes could be made at once, so Suraski was not worried about having to do it again anytime soon.

To some in the conversation, P++ was reminiscent of the Hack language, which is a fork of PHP created at Facebook. This concern is addressed in the FAQ, where Suraski essentially said that things will work out differently because it's the PHP community doing the work. Hack is a single-company project, the FAQ reads, and is not as widely distributed as PHP is. The P++ language, instead, would come automatically with a future version of PHP, so it would be there, waiting, whenever new developers wanted to try it.

What polarization?

What may well turn out to be the majority view, though, was well expressed by Arvids Godjuks, who seems to feel that the entire conception of the problem is wrong. The division described by Suraski does not really exist, Godjuks said; instead, almost all developers are interested in both compatibility and language evolution. The right thing to do is to continue, as the community has done so far, to find a balance between those two requirements:

Instead, Godjuks said, splitting the language would force developers to choose between two versions of PHP, neither of which has the flexibility found in current PHP. One of those two versions would probably wither and die. This point of view was supported in the only post by Rasmus Lerdorf in the thread; Lerdorf, of course, is the creator of PHP. He said:

The discussion is far from resolved at this point, but perhaps some indication of the community's feeling can be found in this poll asking whether the P++ idea is worth pursuing. As of this writing, there are zero votes in favor and 28 opposed (including Suraski, who described the poll as "a false choice").

All told, the P++ idea would appear to be fighting a strong headwind in the community; unless something changes, it seems that it will be hard to build a critical mass of developers interested in making it happen. The discussion will not be wasted, though, if it helps to focus the community's collective mind on how it wants to see the language develop in the coming years. Supporting existing code and keeping the language relevant into the future are both important goals; if the PHP community can find a way to balance those priorities, the language may well continue to thrive for a long time.