====== PHP RFC: Coercing array keys in strict mode deprecation ======
  * Version: 0.1
  * Date: 2017-07-27
  * Authors: Wes (Twitter@WesNetmo)
  * Status: Draft
  * First Published at: https://wiki.php.net/rfc/non_coercing_array_keys_in_strict_mode

===== Proposal =====

This RFC proposes to emit a strict-standards deprecation notice when PHP would coerce array keys' types (e.g. float to int), in case the page uses ''strict_types = 1''.

For example:

<code php>
<?php declare(strict_types = 1);
$array = [];
$array[42.42] = 123;
// 7.3+ Deprecated / Strict Standards: invalid key float(42.42), assuming int(42)
// 8.0+ TypeError invalid array key type "float", expecting int or string
</code>

Except the emitted notice, code will continue to behave as it does currently, until the notice is removed and replaced with a ''TypeError'' in PHP 8.0. If the RFC is accepted, the removal version is binding, but an RFC to block the removal could be used if considered necessary.


===== Impact on generics =====
This proposal is friends with generics, as this change won't directly influence future decisions about them.

For example, arrays could be declared as ''Array<KT, CT> where KT is mixed and CT is mixed'' thus allowing any key type to be used.

However in non-strict, people will continue to rely on coercion of keys, so when type arguments are not specified, the array "constructors" could continue to default to ''<int|string, mixed>''.

<code php>
$array = [22.22 => 123, "foo" => "bar"];
$array = array(22.22 => 123, "foo" => "bar");

// will be equivalent (at least in non-strict mode) to:

$array = <int|string, mixed>[22.22 => 123, "foo" => "bar"];
$array = array<int|string, mixed>(22.22 => 123, "foo" => "bar");
</code>

If non-strict users desire it, in future this can be changed so that type arguments would default to ''<mixed, mixed>'' instead. This would have the effect of eliminating the coercion also in non-strict mode, unless code is changed to explicitly define the type arguments (i.e. from ''[]'' to ''<int|string, mixed>'', which would bring the coercion back). 

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

===== Proposed PHP Version(s) =====
PHP 7.3

===== Open Issues =====
N/A

===== Voting =====
2/3 majority required

===== Patches and Tests =====
N/A

===== References =====
Discussion: [[http://google.com]]