[PHP] heredoc

Please can someone advise me on heredoc and its shortcommings, I am designing a complex site and elected to use DIV's as opposed to frames. Heredoc seems to be ideal in that I can do all processing first and then layout with relative ease. I was wondering if it was acceptable to use and

[PHP] Automating PHP email

I am creating a PHP/mySQL site that enables members to set criteria for email notification As my site changes and clients criteria are met they need to be notified. I can generate a list of email address and info quite simply using mySQL My question is how to trigger or initiate this process