change a script written in php(only experts)

I need you to change a PHP script. it is basically a scraper which scrapes data from a website and stores in my [login to view URL] is working fine but I need one more feature in that if an error comes while scraping like website goes down for some time or any other error it should be able to check the files which have been scraped already and should start from the last point where it was before the [login to view URL] an error comes in I will reload the page on my browser and it should resume not restart from beginning. I am using wamp to run this script on my local PC Thanks Note: I need this done within two hours [login to view URL] you can not do this in two hours do not apply