PHP 8 reference · Array Functions

PHP array_is_list() Function

Check whether an array's keys are 0, 1, 2… in order, so it would encode as a JSON array. Added in PHP 8.1.

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Syntax

array_is_list(array $array): bool

Parameter	Description
`array`	The input array.

true if the keys are consecutive integers from 0.

Lists and mapsTry it yourself

<?php
var_dump(array_is_list(["a", "b"]));
var_dump(array_is_list([1 => "a", 2 => "b"]));
var_dump(array_is_list([]));

Output

bool(true)
bool(false)
bool(true)

Why filtered arrays become JSON objectsTry it yourself

<?php
$filtered = array_filter([1, 2, 3, 4], fn($n) => $n > 2);
var_dump(array_is_list($filtered));
echo json_encode($filtered), "\n";

Output

bool(false)
{"2":3,"3":4}

Version	Change
PHP 8.1	Added

array_values() · Return all the values of an array as a list re-indexed from 0. Often used after array_filter() or unset().
array_filter() · Keep only the elements for which a callback returns true. Without a callback it removes empty values; keys are kept.
PHP Arrays · tutorial
PHP Array Functions · tutorial