InvalidCast

A cast from an array or object to a scalar type (int, float, or string) always produces a meaningless result. For example, casting an array to int always gives 0 or 1; casting an array to string always gives "Array" and triggers a notice in PHP 8.

Example

<?php
/** @param array $data */
function process(array $data): int {
    return (int) $data; // always 0 (empty) or 1 (non-empty), never the intended value
}

How to fix

Use an appropriate function instead of a cast (e.g. count() for length, implode() for string, array_sum() for numeric aggregation).

<?php
/** @param array $data */
function process(array $data): int {
    return count($data);
}