This is a function to protect email addresses on your website from bots or spiders that harvest email addresses for spam purposes; it uses a substitution cipher generating a unique key for every page load.
PHP encrypts your email address and generates javascript to decrypt it because most bots and spiders can’t execute javascript. A visitor of your web page will not notice this as long as they have javascript enabled, otherwise they will see “[javascript protected email address]”
As the script contains quite a lot of special characters, a downloadable version is available here
Usage
echo hide_email(‘test@test.com’);
Further reading
Ross Killen’s implementation here
Methods to hide email addresses in page source here