Automatic conversion of false to array is deprecated¶

Description¶

The array syntax $variable[index] is only available for arrays and strings. Yet, false is an edge case: PHP used to convert automatically, and silently, the boolean to array, when that syntax was used. This is called autovivification.

The other boolean, true behaves the same way, with a different error message.

This feature is used to initialize variables with false, and then convert it to array as needed.

Since PHP 8.1, it is a deprecated behavior.

Example¶

<?php

$variable = false;
$variable[0] = 1;
// $variable is now an array

?>

Solutions¶

Use an empty array as default value.
Test the type of the variable before using it as an array.