How to implement exchange rate in PHP? [closed]

Question

How does major sites implement this?

Do they hardcode the rate or look it up each time?

Answer 1

An idea would be :

• to call some external API regularly, to always have some fresh exchange rate (I don't know how often this can change -- but looking the rate up once every couple of minutes should do)
  • This could be done via some sort of cron job, independantly of your web-application that uses this exchange rate
• and to keep the exchange rate in cache for a couple of minutes :
  • so you don't call the external API too often
  • and don't rely on it too much (i.e. your site will still work if the site you're fetching the rate from is down for a couple of minutes -- and if it takes time to fetch that data, it won't slow your website down, as it's fetched regularly by a cron job)