Automated Scripts, Automating game script. Options

[nerotech]

Hello,

I'm interested in developing an online strategy game using php, I've completed the design document, and am currently in the process of designing class hierarchies.

However, I'm not quite sure how i would automate game updating such as adding gold to a players colony every x amount of minutes, or gathering x amount of resources every x minutes.

How would i go about doing this?