rfc:deprecations_php_7_1

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PHP RFC: Deprecations for PHP 7.1

  • Date: 2015-12-28
  • Author: Nikita Popov nikic@php.net
  • Status: Under Discussion

Introduction

This is a draft RFC for multiple deprecations targeting PHP 7.1. The RFC proposes to deprecate the listed functionality in PHP 7.1 and remove it no later than in PHP 8.0.

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

  • __autoload
  • $php_errormsg
  • create_function()
  • rand() and srand()

Proposal

__autoload

The magic __autoload function has been superseded by spl_autoload_register in PHP 5.1 and its use discouraged in the documentation. One primary advantage of spl_autoload_register() is the ability to provide multiple chained autoloaders, thus easing library interoperability. Both mechanism are mutually exclusive, i.e. code using __autoload() cannot interoperate with code using spl_autoload_register(). As the latter is much more commonly used and also employed by Composer, the __autoload() mechanism has only very limited applicability nowadays.

Proposed action: A deprecation notice is thrown when a global function with name __autoload() is encountered during compilation.

$php_errormsg

The $php_errormsg variable is created in the local scope whenever a non-fatal error is thrown, if the track_errors ini setting is enabled (disabled by default) and the error has not been consumed by an error handler.

Apart from being ini-dependent language behavior, this behavior is highly magic and the error_get_last function provides a cleaner way of retrieving the last error. Since PHP 7 additionally the error_clear_last function is available, thus covering the last possible use-cases for $php_errormsg without magic scope manipulation.

Proposed action: A deprecation notice is thrown if the track_errors ini setting is enabled.

create_function()

create_function() is a thin wrapper around the eval() language construct, allowing the creation of a function with a generated function name and the argument list and body code provided as string arguments. Before the introduction of closures in PHP 5.3 it provided a way to create something akin to lambda functions.

Due to the nature of its operation create_function(), apart from being a potential source of security issues, has very bad performance and memory usage characteristics and the use of real closures is in every way preferable.

Proposed action: Mark the function as deprecated, thus issuing a deprecation notice on every call.

rand() and srand()

The rand() and srand() functions expose the libc random number generator (and its seeding functionality) to PHP. The output and quality of this random number generator is system dependent. Notably, on Windows rand() can only generate at most 32767 unique values for any value range (if the value range includes more than 32767 numbers, some numbers will never be returned). Furthermore Windows uses a very low quality linear congruential generator with bad statistical properties (it's so bad you can see the non-uniformity with the naked eye).

As alternatives to these functions, PHP provides mt_rand() and mt_srand(), which are based on a 32-bit MT19937 algorithm. While not ideal (it generates at most 2147483647 unique values, even on 64-bit platforms), mt_rand() is strictly superior to rand() and does not have a platform dependence. It should always be preferred over rand().

Proposed action: Mark these functions as deprecated, thus issuing a deprecation notice on every call.

Backward Incompatible Changes

For PHP 7.1 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.

Patches and Tests

The patches for these deprecations are for the most part trivial, as such they will be provided once the RFC is accepted (or portions of it).

Rejected deprecations

The following section lists features that have been suggested for deprecation, but have not been included in this RFC for the outlined reasons.

$http_response_header

The $http_repsonse_header variable is created in the local scope if an HTTP request is performed, for example through file_get_contents(). It contains an array of HTTP response headers.

The motivations for removing this functionality are similar to those of $php_errormsg, so it would seem reasonable to deprecate them at the same time. However, unlike $php_errormsg there exist no simple alternatives to $http_response_header. The get_headers function returns only the headers, but not the response body. Getting both requires, to my knowledge, a combination of fopen(), stream_get_contents() and reading the wrapper_data from stream_get_meta_data().

rfc/deprecations_php_7_1.1455800405.txt.gz · Last modified: 2017/09/22 13:28 (external edit)