Can anybody recommend the best method of causing a non-triggered event to occur on a regular basis within or for a web-based application? I would like to send out an e-mail regularly (say, daily) to individuals based on data stored in a MySQL database. All existing interaction with this database is accomplished via PHP. I figure that I have two choices:

a. Use a cron job. b. Have a frequently-called function check the current date and time. If it is within certain parameters, call the function that will cause the e-mail to go out.

I don't like the former, because it will make it harder for people to install this application. The latter is wasteful. Am I missing a third possibility?