No Clue: Automatic MySQL Queries

I've been pondering something for a long time here, but never really knew the right question to ask, or how to word it... so I never even know what to search for. So I honestly have no idea what I'm asking or if this is even under the right topic. What I'm looking for is answers, links, tutorials, or just some words I can search for to help me do the following:

I have a MySQL database filled with accounts. People have to pay to get these accounts. All the accounts are set to expire on different days. I need to send an e-mail out to accounts, for example, to let them know they're expiring, say, a month before this will occur. Right now the only way I know to do this is to have MySQL queries on a PHP page that, every time the page is loaded, runs through all the accounts, checks their expirations, and sends emails to those that need it. I know there has to be a way to have this happen automatically without having to load a PHP page every day, for example.