PHP RFC: "var" Deprecation

• Date: 2016-02-20
• Author: Colin O'Dell colinodell@php.net
• Status: Draft
• Discussion: http://markmail.org/message/wn3ykdwgplfctho7

var is currently a simple alias for public. Both keywords provide identical functionality. This RFC therefore proposes the deprecation of var in favor of public.

PHP 4 introduced the var keyword as the only means to declare class properties.

PHP 5 added the public, protected, and private keywords for declaring these properties with a certain visibility level. To quote the documentation:

“The PHP 4 method of declaring a variable with the var keyword [was] supported for compatibility reasons (as a synonym for the public keyword”

(emphasis added)

This alias was left intact for PHP 7.

This RFC proposes that var be deprecated in PHP 7.1 and its functionality removed in PHP 8.0. var would remain a reserved word in PHP 8.0 for potential future usage.

The primary reason for introducing this change is to eliminate duplicate functionality in the language. Both var and public work identically, so do we really need two different keywords which do exactly the same thing?

Of the top X,000 packages on Packagist, only X use var, thus confirming that its usage is relatively low. This means fewer people will be impacted by this change.

var is a legacy feature from PHP 4 which has been superseded by the visibility keywords. It was kept in PHP 5+ for backwards-compatibility. Removing it would help clean up the lesser-used legacy bits of the language.

There is precedent for deprecating (and eventually removing) other legacy features with modern equivalents in major releases:

• PHP 4 constructors were removed in 7.0
• Alternative PHP tags were removed in 7.0
• Several other previously-deprecated features were removed in 7.0

PHP 8.0 is at least a few years away. Deprecating this now (rather than later) would provide developers with sufficient notice that their code may need to be modified to work on 8.0.

Because var is currently an alias for public, updating older code is as simple as replacing var with public everywhere it appears. A utility script has been provided with this RFC to aid with the transition.

There are no technical issues with the current implementation of var, and therefore no strong need to remove it.

PHP 4 classes will no longer function as-is in PHP 8.0. Furthermore, any classes written in PHP 5.x or 7.x may also break in 8.0 if they use var. BC breaks should not be taken lightly.

This change does not introduce any new functionality or other benefit for developers. Those who are not using var will see no impact. Those who do use var will need to update their code.

PHP 7.1 - 7.x: usages of var will raise a deprecation notice but otherwise work as-is.

PHP 8.0: Usages of var will throw a parse error.

An upgrade tool is provided which replaces all instances of var with public.

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Classes which only use the PHP 5 style keywords for declaring properties (public, protected, and private) would be unaffected.

Reserving the var keyword may allow it to be used for new functionality in 8.0 and beyond.

As this is a language change, this RFC requires a 2/3 majority to pass.

No patch has been created yet.

• http://markmail.org/message/wn3ykdwgplfctho7