PHP 8.1 Introduces the array_is_list() Function

This article is a translation of a blog post originally published at stitcher.io , describing a new feature added in PHP 8.1.

Developers often need to verify that an array’s keys are ordered numerically from 0 without gaps, a check that influences how json_encode decides to encode the array as a JSON list or object.

PHP 8.1 adds a native function array_is_list() that returns true when the array meets these list semantics and false otherwise.

$list = ["a", "b", "c"];<br/>array_is_list($list); // true<br/><br/>$notAList = [1 => "a", 2 => "b", 3 => "c"];<br/>array_is_list($notAList); // false<br/><br/>$alsoNotAList = ["a" => "a", "b" => "b", "c" => "c"];<br/>array_is_list($alsoNotAList); // false

For full details see the RFC: https://wiki.php.net/rfc/is_list .

Related PHP 8.1 feature articles include:

Enums

Readonly properties

Initializers

Fibers with a grain of salt

String-key unpacking

Pure intersection types