PHP
Functions
https://secure.php.net/manual/en/function.strip-tags.php
WordPress
Functions
https://codex.wordpress.org/Function_Reference/sanitize_title
https://codex.wordpress.org/Function_Reference/wp_unique_post_slug
Assignment
Create a plugin that will set a human-friendly slug on posts that are saved without a title. Ideally, the slug will consist of the first five words of the post content.