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Date: Mon, 14 Mar 2022 17:20:24 -0400
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Cc: Kamil Tekiela <tekiela246@gmail.com>,
 PHP internals <internals@lists.php.net>
To: Lynn <kjarli@gmail.com>
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 <20220312031138.5e0669a4@platypus>
 <CANS-=pfAvb2T9HS-+T-CpnUDnnbp-GgSeYnHCive+PRB_sJC5A@mail.gmail.com>
 <5E019DDC-43D8-4676-9AA6-FBEF36A92FEF@newclarity.net>
 <CANS-=pc2dANwsVVfUxvPZVFJzVA8HDaSz2mbyJDdocdULK7pTg@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC][Under discussion] Deprecate ${} string
 interpolation
From: mike@newclarity.net (Mike Schinkel)

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> On Mar 14, 2022, at 3:20 PM, Lynn <kjarli@gmail.com> wrote:
>=20
> On Mon, Mar 14, 2022 at 8:04 PM Mike Schinkel <mike@newclarity.net =
<mailto:mike@newclarity.net>> wrote:
>=20
> Variable variables provide functionality[1] that if removed would =
force major rewrites of PHP applications that were architected in a way =
that depends on that functionality.=20
> And while probably between 90% and 99% of the time when someone uses =
variable variables there are better alternatives, variable variables =
make certain code possible that would be impossible without them.=20

> Do you have examples where this is the case?=20

Most of these things cannot be done without the functionality provided =
by variable variables. However a few are examples could be handled =
differently but would require significant rewrite to fix without a new =
get_value_from_variable_name() function.  Either way, these are just =
from the first few pages of those 162.2k results on SourceGraph.com =
<http://sourcegroup.com/>:

=
https://github.com/microsoft/sql-server-samples/blob/master/samples/develo=
pment-frameworks/laravel/vendor/jeremeamia/SuperClosure/src/SerializableCl=
osure.php#L200-L208 =
<https://github.com/microsoft/sql-server-samples/blob/master/samples/devel=
opment-frameworks/laravel/vendor/jeremeamia/SuperClosure/src/SerializableC=
losure.php#L200-L208>
=
https://github.com/mockery/mockery/blob/master/library/Mockery/Generator/S=
tringManipulation/Pass/MethodDefinitionPass.php#L151 =
<https://github.com/mockery/mockery/blob/master/library/Mockery/Generator/=
StringManipulation/Pass/MethodDefinitionPass.php#L151>
=
https://github.com/vlucas/phpdotenv/blob/master/tests/Dotenv/DotenvTest.ph=
p#L251 =
<https://github.com/vlucas/phpdotenv/blob/master/tests/Dotenv/DotenvTest.p=
hp#L251>
=
https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/PSR=
12/Tests/Classes/ClassInstantiationUnitTest.inc#L34-L38 =
<https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Standards/PS=
R12/Tests/Classes/ClassInstantiationUnitTest.inc#L34-L384>
https://github.com/kanaka/mal/blob/master/impls/php/interop.php#L19 =
<https://github.com/kanaka/mal/blob/master/impls/php/interop.php#L19>
=
https://github.com/moodle/moodle/blob/master/mod/data/tests/lib_test.php#L=
1293 =
<https://github.com/moodle/moodle/blob/master/mod/data/tests/lib_test.php#=
L1293>
=
https://github.com/moodle/moodle/blob/master/mod/data/tests/generator_test=
.php?L105#L104 =
<https://github.com/moodle/moodle/blob/master/mod/data/tests/generator_tes=
t.php?L105#L104>
=
https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/master/tests/Fixer/Funct=
ionNotation/StaticLambdaFixerTest.php#L236 =
<https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/master/tests/Fixer/Func=
tionNotation/StaticLambdaFixerTest.php#L236>
=
https://github.com/phpipam/phpipam/blob/master/functions/PEAR/Net/Ping.php=
#L284 =
<https://github.com/phpipam/phpipam/blob/master/functions/PEAR/Net/Ping.ph=
p#L284>
=
https://github.com/api-platform/core/blob/main/src/Core/Annotation/ApiProp=
erty.php#L154-L159 =
<https://github.com/api-platform/core/blob/main/src/Core/Annotation/ApiPro=
perty.php#L154-L159>
=
https://github.com/wp-cli/wp-cli/blob/master/php/WP_CLI/Runner.php#L1285-L=
1287 =
<https://github.com/wp-cli/wp-cli/blob/master/php/WP_CLI/Runner.php#L1285-=
L1287>
=
https://github.com/phpmyadmin/phpmyadmin/blob/master/libraries/classes/Dat=
abase/Qbe.php#L878-L879 =
<https://github.com/phpmyadmin/phpmyadmin/blob/master/libraries/classes/Da=
tabase/Qbe.php#L878-L879>
=
https://github.com/PrestaShop/PrestaShop/blob/develop/classes/SpecificPric=
e.php#L474 =
<https://github.com/PrestaShop/PrestaShop/blob/develop/classes/SpecificPri=
ce.php#L474>


> Using arrays is a compatible replacement as far as I know, and I =
highly doubt these kinds of hacks are necessary.

"Necessary" is a judgement call.  If you never do meta-programming in =
PHP then these _techniques_ =E2=80=94 calling them "hacks" is a bit =
incendiary =E2=80=94 would not ever seem necessary.=20

However if a developer does work on projects that by-requirement =
leverage meta-programming then variable variables are a tool in one's =
toolkit that one would be hobbled without.

An area where I have seen them required is in theming where the CMS or =
plugin vendor wants to make it easier on the themer by creating =
dynamically-named variables in scope and then including a PHP file =
intended to be used as a template, and the in other functions being able =
to access those dynamically-named variables.

Other areas are in developer tools written in PHP for PHP developers.

That said, are you objecting to the "variable variable" syntax, or more =
broadly to the ability to access the value of a variable given its name =
(as a new function could provide)?

-Mike

P.S. BTW, I agree that if a developer can avoid variable variables there =
would be doing themselves and future maintainers a big favor. I am only =
commenting because in rare cases variable variables provide a capability =
that you cannot achieved another way.  But if PHP provides that other =
way by way of a function then the only concern is BC breakage for those =
who have used the technique.






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