Cron job for an existing crawler

I have currently a crawler which scrapes house properties from a rental website. What I need nnow is a script which is a combination of a crob job and PHP. This is what needs to be done: There are two files from the crawler: [login to view URL] and [login to view URL] [login to view URL] has a function called get_city($city). What it does it goes to the page of the city on the rental website. For every entry on all the pages of that city it calls a function from [login to view URL] called scrape_entry($url). We then have a list of cities divided into 7 arrays (monday, tuesday, wednesday, thursday, friday, saturday, sunday). What needs to be done then is the following: Every two weeks on the day of the array the script should check the cities in that array and call the get_city($city) function from the [login to view URL] file. We'd like to do it this way because we don't want to cause a heavy load on the server of the rental website. If you have better ideas or suggestions, please let me know.