PHP: rfc:language-constructs-syntax-changes

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====== PHP RFC: Language Constructs Syntax Changes ======
  * Version: 0.9
  * Date: 2020-07-04
  * Author: Michał Marcin Brzuchalski, <brzuchal@php.net>
  * Status: Withdrawn
  * Target Version: PHP 8.0
  * First Published at: http://wiki.php.net/rfc/language-constructs-syntax-changes

Language constructs syntax changes regarding the need for parentheses for ''declare'' and ''_''''_halt_compiler'' stamenents.

===== Introduction =====
In 25yrs history, many language constructs were allowed in different forms depending on the context.

A ''declare'' statement which is a language construct and not a function cannot be used as a function 
nor in write context but require parentheses while some language constructs like ''print'' can be used as a function 
but they don't require parentheses no matter of context.

The same goes to ''_''''_halt_compiler'' statement which cannot
be used as a function nor in write context because it's not an expression and only looks like that.


===== Proposal =====
The proposal is to bring more sanity into the language by relaxing restrictions in some language constructs.

==== Allow skip of parentheses for declare ====
A ''declare'' statement is not a function but a language construct and cannot be used as an expression.
Therefore the proposal is to allow use it without parentheses:
<code php>
declare strict_types = 1;
declare ticks = 1;
declare encoding = 'ISO-8859-1';
</code>

Allowing also to group them into one statement:
<code php>
declare strict_types = 1, ticks = 1, encoding = 'ISO-8859-1';
</code>

<blockquote>This proposal doesn't influence a declare syntax of ticks with additional statement block!</blockquote>

==== Allow to skip parentheses for compiler halt ====
A language construct like ''_''''_halt_compiler'' is a statement and cannot be use used as an expression.
This language construct stops parsing.
It looks like a function and it always requires parentheses but it can never be used as a function nor in write context,
 cause it's considered a syntax error.

<code php>
$foo = __halt_compiler(); // syntax error
</code>

Therefore the proposal is to allow skip of parentheses as in the example:
<code php>
__halt_compiler;
</code>

===== Backward Incompatible Changes =====
None.

===== Proposed PHP Version(s) =====
PHP 8.0.

===== RFC Impact =====
==== To SAPIs ====
None.

==== To Existing Extensions ====
None.

==== To Opcache ====
None.

==== New Constants ====
None.

===== Proposed Voting Choices =====
This is a language change and requires 2/3 majority in 4 separate pools with simple Yes/No options.

===== Implementation =====
  * [[https://github.com/php/php-src/pull/5808|Allow declare w/o parentheses]]
  * [[https://github.com/php/php-src/pull/5809|Allow __halt_compiler w/o parentheses]]
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