Expiry time code for php

Hello dear, i am a student and i like to study more about php. i have some technical problems and i requesting you to help for this please. I have a PHP file and i coded, without using database. i like to set an expiry time for that php file. what is required is: once we set a expiry time, after the expiry date (expired), it must be give a warning or status message as the script expired. For example: i set expiry date (time) as "24/04/2011" and expired status as "This script expired", after 24/04/2011, if user go to the page the status must be show. it's means the functions won't work but the status will be show in the internet browsers. Do you have any idea how to code for this ? Please give me some sample for > "24/04/2011" and status as "This script expired". NOTE: This script not connect with any database. and running in linux server. If you can help me, i can improve my php knowledge, Please try to help me. Thank you in advance. Best regards, Thomas N.