Cron作业检查页面是否有特定的更改，如果是，则发送mail（）

I am setting up a CRON to detect a change on a page. The issue I am having is pointing more to server side but I would like some others to look at the code and see if any obvious problems stick out that would hinder the CRON from running right. The CRON runs the script and works some of the time on its own, the results are either 100% correct or the email is delayed with the wrong time stamp coming from $nws_timestamp in the message. I am setting up a CRON to detect a change on a