Parse error: syntax error, unexpected '[' in ./Classes/Options.php on line 38

I just upgraded the plugin to version 2.0.0 and immediately I got the mentioned syntax error on the following function in Options.php:

public function get_option( $option_name )
{
if (! $this->has_option( $option_name ) ) {
return $this->get_defaults()[$option_name];
}

return $this->options[$option_name];
}

Line 38 is the then statement there in the middle.

https://ww.wp.xz.cn/plugins/php-code-for-posts/