PHP: rfc:is_assoc_array

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====== PHP RFC: Add is_assoc_array ======
  * Version: 0.9
  * Date: 2026-02-21
  * Author: Muhammed Arshid, arshidkv12@gmail.com
  * Status: Under Discussion
  * Implementation: https://github.com/php/php-src/pull/21266

===== Introduction =====
PHP arrays can behave as both lists and associative maps.
Currently, PHP has no built-in function to detect whether an array is associative.

Userland frameworks implement helper functions for this purpose. Adding a native function improves performance, readability, and consistency.

<PHP>
<?php

$data = ['a'=> 1, 'b' => 2];
var_dump(is_assoc_array($data)); // bool(true)

?>
</PHP>

===== Proposal =====
Add a new core function:

<PHP>
<?php

function is_assoc_array(array $array): bool {}

?>
</PHP>

This function determines whether an array is associative based on PHP’s internal array storage.

An array is considered associative when it is not a packed array internally.

==== Examples ====

<PHP>
<?php

var_dump(is_assoc_array(['a' => 'a', 0 => 'b']));   // true
var_dump(is_assoc_array([1 => 'a', 0 => 'b']));     // true
var_dump(is_assoc_array([1 => 'a', 2 => 'b']));     // true
var_dump(is_assoc_array([0 => 'a', 1 => 'b']));     // false
var_dump(is_assoc_array(['a', 'b']));               // false

var_dump(is_assoc_array([]));                      // false (empty array not associative)
var_dump(is_assoc_array([1, 2, 3]));               // false
var_dump(is_assoc_array(['foo', 2, 3]));           // false

var_dump(is_assoc_array([0 => 'foo', 'bar']));        // true
var_dump(is_assoc_array([1 => 'foo', 'bar']));        // true
var_dump(is_assoc_array([0 => 'foo', 'bar' => 'baz']));     // true
var_dump(is_assoc_array([0 => 'foo', 2 => 'bar']));        // true
var_dump(is_assoc_array(['foo' => 'bar', 'baz' => 'qux'])); // true

?>
</PHP>

===== Why This is Needed =====

    * Developers frequently need to check array type:
    * JSON encoding logic
    * API validation
    * Config parsing
    * Data normalization

Userland solutions are slower and inconsistent.
Native implementation provides:
    * O(1) performance
    * Standard behavior
    * Cleaner code

===== Backward Incompatible Changes =====
None
This adds a new function only.

===== Proposed PHP Version(s) =====
PHP 8.6

===== RFC Impact =====
There may be conflicts if userland code already defines is_assoc_array().
Such functions can be replaced with the built-in implementation.

No impact to SAPIs or OPcache.

===== Voting Choices =====
Pick a title that reflects the concrete choice people will vote on. 

Please consult [[https://github.com/php/policies/blob/main/feature-proposals.rst#voting-phase|the php/policies repository]] for the current voting guidelines.

----

Primary Vote requiring a 2/3 majority to accept the RFC:

<doodle title="Implement $feature as outlined in the RFC?" voteType="single" closed="true" closeon="2026-01-01T15:30:00Z">
   * Yes
   * No
   * Abstain
</doodle>

===== Patches and Tests =====
Links to proof of concept PR.

If there is no patch, make it clear who will create a patch, or whether a volunteer to help with implementation is needed.

===== Implementation =====
After the RFC is implemented, this section should contain:
  - the version(s) it was merged into
  - a link to the git commit(s)
  - a link to the PHP manual entry for the feature

===== References =====
Links to external references, discussions, or RFCs.

===== Rejected Features =====
Keep this updated with features that were discussed on the mail lists.

===== Changelog =====
If there are major changes to the initial proposal, please include a short summary with a date or a link to the mailing list announcement here, as not everyone has access to the wikis' version history.
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