invariant.php

<?php
/**
 * Use invariant() to assert state which your program assumes to be true.
 *
 * @throws Exception
 */
function invariant(mixed $condition, string $message = 'Invariant Violation', ...$params): void
{
    if (! $condition) {
        if (func_num_args() > 2) {
            $message = sprintf($message, ...$params);
        }

        throw new Exception($message);
    }
}