Possibility for on-site validity selfcheck

Is there a practical way to configure a site to perform a markup validation selfcheck, by means of html/php variables or other forms of scripting?

Related Problem: Sites that undergo source code editing might lose validity, but forget to re-check, and as a result keep the validity bagde.
Possible Solution: An on-site script that can check an off-site variable (at the W3C-validator), might automate markup validation and kan regulate the appearance of the validity badge.