[TYPO3-english] Run a task from typo3?

[Alexandra Constantin]

I have to send an e-mail to the user after he created an event.

First time I have created a task from the backend and set from the form the date and the hour and the e-mail was sent, but now I want to send the e-mail from php code automatically..
How can I schedule a task to run at a certain time from php code in my controller and not from the Backend -> Scheduler but have the same results?
Thank you!