PHP: rfc:deprecate_php_short_tags_v2

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====== PHP RFC: Deprecate short open tags, again ======
  * Date: 2019-07-23
  * Author: George Peter Banyard <girgias@php.net>, Nikita Popov <nikic@php.net>
  * Status: Declined
  * Target version: PHP 7.4
  * Implementation: https://github.com/php/php-src/pull/4263
  * Counterargument: https://wiki.php.net/rfc/counterargument/deprecate_php_short_tags


<blockquote>This RFC has been granted an exemption to land in PHP 7.4 after feature freeze by the release managers for PHP 7.4 
Derick Rethans <derick@php.net> and Peter Kokot <petk@php.net></blockquote>

===== Introduction =====

In addition to ''<?php'', PHP allows opening PHP scripts with just ''<?'' if the ''short_open_tag'' ini setting is enabled. This RFC proposes to deprecate and remove this configuration-dependent syntax.

The deprecation of short open tags was previously accepted as part of [[rfc:deprecate_php_short_tags]]. However, a substantial amount of discussion was generated only after the RFC has been accepted, and some concerns were raised over the implementation approach. This RFC supersedes the previous one and proposes a different deprecation approach.

===== Proposal =====

==== Current state ====

Currently the ''<?'' short open tag is controlled by the ''short_open_tag'' ini setting. This ini setting is //enabled// by default (if no ini files is used), but //disabled// in both ''php.ini-development'' and ''php.ini-production''.

If ''short_open_tag'' is enabled ''<?'' is interpreted as the start of a PHP context. If ''short_open_tag'' is disabled, ''<?'' is interpreted as literal text without special meaning.

The ''<?='' combined opening and echo tag is not controlled by ''short_open_tag''. It is always available, and will continue to be always available after this RFC.

==== Motivation for removal ====

There are two primary motivations for removing short open tags:

First, ''short_open_tag'' is an ini setting that control core language syntax. This means that their use is not possible in portable code, because the code author does not necessarily have the necessary control over the configuration of the deployment environment. Worse than that, code using short open tags deployed on a server using ''short_open_tag=0'' will leak application code, because short open tags are silently ignored.

Nowadays the PHP project has a hard policy against ini settings that affect core language behavior. Short open tags are one of the final leftovers from the time before this policy was in place.

Second, short open tags are not compatible with XML declarations ''<?xml ... ?>'' and XML processing instructions ''<?pi ... ?>''. This means that the use of XML in template files is also non-portable: If deployed in an environment with ''short_open_tag=1'', it will cause a syntax error. (Technically a processing instruction could also coincide with valid PHP code and be executed as such, but this is unlikely.)

==== Deprecation and removal proposal ====

In PHP 7.4 ''short_open_tag'' remains enabled by default: Changing the default could result in code leaks during upgrades, if people rely on the default value rather than explicitly enabling them. Instead:

  * If ''short_open_tag'' is enabled //and// ''<?'' is used, a single deprecation notice is emitted.
  * If ''short_open_tag'' is enabled, but ''<?'' is never used, no deprecation notice is emitted (as before).
  * If ''short_open_tag'' is disabled, ''<?'' has no special meaning and is interpreted as plain text (as before).

In PHP 8.0 the deprecation notice is converted into a parse error:

  * If ''short_open_tag'' is enabled, the use of ''<?'' is a parse error.
  * If ''short_open_tag'' is disabled, ''<?'' has no special meaning (as before).

In PHP 9.0 support for short_open_tag is dropped entirely:

  * ''<?'' never has special meaning, it is always interpreted as plain text.

This deprecation and removal plan avoids unintentional code leaks during PHP version upgrades.

==== Migration ====

While a migration of a legacy codebase from short open tags to standard ''<?php'' tags may seem daunting, it can be reliably automated.

For example, the ''"full_opening_tag"'' fixer from [[https://cs.symfony.com/|PHP-CS Fixer]] can be used. Other coding style and compatibility fixers also provide this functionality.

===== Backward Incompatible Changes =====

Short open tags ''<?'' will be removed. ''<?='' continues to always be available.

===== Counterargument =====
A counterargument for this deprecation proposal is [[https://wiki.php.net/rfc/counterargument/deprecate_php_short_tags
|available here]].  It is supported by Rasmus Lerdorf, Zeev Suraski, Dmitry Stogov, Sara Golemon.

===== Vote =====
Require a 2/3 majority as per the Voting RFC.

Voting started on 2019-08-06 at 11:30 UTC and is expected to last two (2) weeks until 2019-08-20

<doodle title="Deprecate and remove short open tags as proposed?" auth="girgias" voteType="single" closed="true">
   * Yes
   * No
</doodle>


===== References =====
[[https://externals.io/message/106384|Version 2 (this one) RFC Vote Announcement on Internals (link to External.io)]]\\
[[https://wiki.php.net/rfc/counterargument/deprecate_php_short_tags|Counter arguments to this RFC]]\\
[[https://externals.io/message/106256|Version 2 (this one) RFC Announcement on Internals (link to External.io)]]\\
[[https://externals.io/message/105201|Version 1 of RFC Vote Announcement on Internals (link to External.io)]]\\
[[https://externals.io/message/104922|Version 1 of RFC Announcement on Internals (link to External.io)]]\\
[[https://externals.io/message/104662|Initial feedback on Internals (link to External.io)]]\\
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