The exact string "5640" does not correspond to any official PHP version (e.g., 5.6.40 is a real version, often typed as 5.6.40). Given the context of security research and typos, this article addresses PHP 5.6.40 (the final release of the PHP 5.x branch) and explains how to find verified vulnerability links.
php -v
If it outputs PHP 5.6.40, your server is vulnerable to every link in this article.