$unixseconds = strtotime($mysqldate);
For instance, you can use this to write a timeout script for login failures. Usually, a system should lock after 3-5 consecutive failed login attempts. I save the timestamp after the 5th consecutive login failure, then run a check on this timestamp if the current time is within the ~5-10 minute lockout window. 5 minutes is 300 seconds, 10 minutes is 600 seconds.