PHP: rfc:deprecations_php_7_3

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====== PHP RFC: Deprecations for PHP 7.3 ======
  * Date: 2017-08-02
  * Author: Nikita Popov <nikic@php.net>
  * Status: Implemented (in PHP 7.3)
  * Implementation: https://github.com/php/php-src/pull/3366 (unless other patch linked below)
  * Discussion: https://externals.io/message/102394

===== Introduction =====

This is a draft RFC for multiple deprecations targeting PHP 7.3. The RFC proposes to deprecate the listed functionality in PHP 7.3 and remove it in PHP 8.

The following list provides a short overview of the functionality targeted for deprecation, while more detailed explanation is provided in the Proposal section:

  * Undocumented mbstring function aliases
  * String search functions with integer needle
  * ''fgetss()'' function and ''string.strip_tags'' filter
  * Defining a free-standing ''assert()'' function
  * ''FILTER_FLAG_SCHEME_REQUIRED'' and ''FILTER_FLAG_HOST_REQUIRED'' flags
  * ''pdo_odbc.db2_instance_name'' php.ini directive

===== Proposal =====

Each feature proposed for deprecation is voted separately. Each vote requires a 2/3 majority, independently of whether it is a language or standard library change. All votes refer to deprecation in PHP 7.3 and removal in the next major version (presumably PHP 8.0). The votes close on 2018-07-16.

==== Undocumented mbstring function aliases ====

The functions ''mbregex_encoding'', ''mbereg'', ''mberegi'', ''mbereg_replace'', ''mberegi_replace'', ''mbsplit'', ''mbereg_match'', ''mbereg_search'', ''mbereg_search_pos'', ''mbereg_search_regs'', ''mbereg_search_init'', ''mbereg_search_getregs'', ''mbereg_search_getpos'' and ''mbereg_search_setpos'' are undocumented aliases of the same functions using an ''mb_'' prefix (e.g., ''mb_ereg'').

Proposed action: Mark the functions as deprecated, so that a deprecation notice is emitted on every call. In PHP 8 these aliases will be removed.

<doodle title="Deprecate (and subsequently remove) undocumented mbstring function aliases?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== String search functions with integer needle ====

The following applies to the ''strpos'', ''strrpos'', ''stripos'', ''strripos'', ''strstr'', ''strchr'', ''strrchr'' and ''stristr'' functions. ''strpos'' will be used as a representative example.

String search functions usually operate on a string needle. However, if a non-string is passed, it will be converted to an integer and interpreted as an ASCII codepoint:

<code php>
$str = "There are 10 apples";
var_dump(strpos($str, "10")); // int(10)
var_dump(strpos($str, 10));   // bool(false)
</code>

In a language that relies on transparent type juggling between scalar types, this is problemantic, because the type can easily change depending on the used data source. For example, array keys in PHP are automatically converted to integers, so that using an array key as a ''strpos'' needle may not work correctly, because it is interpreted as an ASCII codepoint rather than a string.

Proposed action: Throw a deprecation warning if a non-string is passed as a needle to ''strpos'' or one of the above-listed functions. The deprecation warning should note that an explicit ''chr'' call may be used instead. In PHP 8 the deprecation warning will be removed and the needle parameter will be changed into a string.

<doodle title="Deprecate (and subsequently remove) integer needles in string search functions?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== fgetss() function and string.strip_tags filter ====

The ''fgetss()'' function and the ''string.strip_tags'' stream filters expose the functionality of ''strip_tags()'' in a streaming matter. The need to support these makes the implementation of ''strip_tags()'' more complicated, as a streaming state machine is necessary. On the other hand, these functions seem to be of very little utility. ''strip_tags()'' itself, due to its limitations and known bugs, already has very few legitimate applications. There is no need to provide native support for streaming application on top of that.

Proposed action: Mark ''fgetss()'', ''gzgetss()'' and ''SplFileObject::fgetss()'' as deprecated, so that a deprecation notice is emitted on every call. Generate a deprecation notice if the ''string.strip_tags'' stream filter is created. In PHP 8 the functions and the stream filter are removed.

<doodle title="Deprecate (and subsequently remove) fgetss() (and variations) and the string.strip_tags filter?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== Defining a free-standing assert() function ====

Since PHP 7.0 the ''assert()'' function is subject to special treatment in the compiler. In particular, calls to ''assert()'' will be elided if ''zend.assertions=-1'' is set. To make this elision of asserts in production systems work reliably, this also applies to unqualified ''assert()'' calls inside namespaces. However, such calls may refer to a namespaced variant of ''assert()'' rather than the global function, and such calls are thus also subjected to ''zend.assertions=-1''. See [[https://bugs.php.net/bug.php?id=75445|Bug #75445]].

To avoid confusion due to this behavior, it is suggested to forbid the definition of free-standing ''assert()'' functions. Methods are unaffected.

Proposed action: Generate a compile-time deprecation warning if an ''assert()'' function is declared. In PHP 8 this becomes a compile-error.

<doodle title="Deprecate (and subsequently remove) support for defining a free-standing assert() function?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== FILTER_FLAG_SCHEME_REQUIRED and FILTER_FLAG_HOST_REQUIRED ====

As of PHP 5.2.1 ''FILTER_VALIDATE_URL'' implies ''FILTER_FLAG_SCHEME_REQUIRED'' and ''FILTER_FLAG_HOST_REQUIRED''. Not only are these constants useless, they also create the incorrect impression that the scheme/host requirement can be disabled.

Proposed action: Generate a deprecation warning if the ''FILTER_FLAG_SCHEME_REQUIRED'' or ''FILTER_FLAG_HOST_REQUIRED'' flags are explicitly set in calls to filter APIs (PHP currently has no mechanism to deprecate the constants themselves). In PHP 8 the constants will be removed.

Implementation: https://github.com/php/php-src/pull/3322

<doodle title="Deprecate (and subsequently remove) FILTER_FLAG_(SCHEME|HOST)_REQUIRED flags?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

==== pdo_odbc.db2_instance_name php.ini directive ====

As of PHP 5.1.1 ''pdo_odbc.db2_instance_name'' was marked as deprecated in the manual, promising removal in a future version of PHP. This ini directive modifies the DB2INSTANCE environment variable for non Windows operating systems, allowing pdo_odbc to make cataloged connections to a DB2 database.

The side effect here is that this setting is process wide and also affects the ODBC extension, which can create some hard to debug situations. Besides this, the PECL package, ibm_db2 seems to implement the exact same behavior which could also conflict.

Proposed action: Add a deprecation notice if the ini directive has a value at module initialization.

Implementations: https://gist.github.com/KalleZ/424ea78492cd5f4c2198cba6b25403d9

<doodle title="Deprecate (and subsequently remove) pdo_odbc.db2_instance_name php.ini directive?" auth="nikic" voteType="single" closed="true">
   * Yes
   * No
</doodle>

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

For PHP 7.3 additional deprecation notices will appear. For PHP 8.0 the previously deprecated functionality will no longer be available.

===== Proposed Voting Choices =====

Each of the bullet points above will get a separate vote. All votes will require a 2/3 supermajority, independently of whether they are language changes or not.
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