src/Pimple/ConfigServiceProvider.php
private function mergeRecursive($existingValue, $newValue, string $path)
    {
        $existingType = gettype($existingValue);
        $newType = gettype($newValue);

        if ($existingType !== $newType) {
            throw new \LogicException(
                sprintf('Type conversion from "%s" to "%s" at path "%s"', $existingType, $newType, $path)
            );
        }

        if ('array' !== $newType) {
            return $newValue;
        }

        foreach ($newValue as $key => $newSubValue) {
            if (!is_string($key)) {
                $existingValue[] = $newSubValue;

                continue;
            }

            if (isset($existingValue[$key])) {
                $subPath = $path.'.'.$key;

                $existingValue[$key] = $this->mergeRecursive($existingValue[$key], $newSubValue, $subPath);
            } else {
                $existingValue[$key] = $newSubValue;
            }
        }

        return $existingValue;
    }
private function mergeRecursive($existingValue, $newValue, string $path)
    {
        $existingType = gettype($existingValue);
        $newType = gettype($newValue);

        if ($existingType !== $newType) {
            throw new \LogicException(
                sprintf('Type conversion from "%s" to "%s" at path "%s"', $existingType, $newType, $path)
            );
        }

        if ('array' !== $newType) {
            return $newValue;
        }

        foreach ($newValue as $key => $newSubValue) {
            if (!is_string($key)) {
                $existingValue[] = $newSubValue;

                continue;
            }

            if (isset($existingValue[$key])) {
                $subPath = $path.'.'.$key;

                $existingValue[$key] = $this->mergeRecursive($existingValue[$key], $newSubValue, $subPath);
            } else {
                $existingValue[$key] = $newSubValue;
            }
        }

        return $existingValue;
    }
@param array|string|float|int|bool $existingValue
@param array|string|float|int|bool $newValue
@param string                      $path

@return array|string|float|int|bool