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RFC: Allow arbitrary expression arguments to empty() and isset()
- Date: 2012-04-12
- Author: Nikita Popov nikic@php.net
- Status: In voting phase
- Original discussion: http://markmail.org/thread/gnci76ugtwda2t42 (Apr 10, 2012 3:53 pm)
- RFC announcement: http://markmail.org/thread/ju2jyrenxkeddrnt (Apr 12, 2012 2:42 pm)
Summary
This RFC proposes to allow arbitrary expressions as arguments to empty()
and isset()
.
What is the current behavior?
Currently empty()
and isset()
only accept variables as arguments. Thus it is possible to write empty($foo)
,
but it is not possible to write empty(foo())
.
Trying to do so results in this not particularly helpful error message: “Can't use function return value in write context”.
For other expressions (not variables and not function calls) a parse error is thrown.
Why was this behavior chosen in the past?
Using empty()
and isset()
on a non-variable was disallowed previously, as the main purpose of these language
constructs is to suppress an error message in case the passed variable does not exist.
As for function calls (and other expressions) it is already known that the value exists, using empty()
/isset()
is
not necessary and !func()
/func() !== null
can be used instead.
Why should we change the behavior?
Even though !func()
and empty(func())
would behave exactly the same, the latter is more readable in certain contexts.
For example if func()
is expected to return an array, it feels more natural to verify it's emptiness using empty()
instead
of !
.
Furthermore the current behavior often is unexpected to newbies. empty()
and isset()
look like functions, so programmers
new to PHP expect them to accept any value (in particular function call results).
Patch
The patch is available as a PR on Github: https://github.com/php/php-src/pull/54
Vote
The previous vote is obsolete and is left here only for reference: