Question

My shopping app needs to do currency conversion, my plan is to use a crontab to grab the latest exchange rates once an hour. My question is whats the best way to store and use this in my CI application. Should I:
– Write it to the DB everytime its run and then grab the rate from the DB evrytime i need to do a conversion
– Do the same but with a text file
– Write it to a constant in the index.php
– Some sort of core or hook file

Whats the most efficient way

Answer 1

The quick & dirty way would be writing a PHP file with the said currencies. You can use var_export() to save them safely.

Config:

$file = '/path/to/currencies.php';

Cronjob:

// get data from API (note: you should use proper functions via CURL)
$currencies = file_get_contents('http://some.api.com/currencies');
// decode data
$currencies = json_decode( currencies );
// export data into PHP format
$currencies = var_export( currencies, true );
// save to file
file_put_contents($file, "<?php\r\n $currencies=".$currencies."; \r\n?>");

Currency Page:

// ensure you get a default something
$currencies = array();
// load data file (note, we use include so we can load it whenever we want)
@include $file;
// output something from array
echo $currencies['EUR'];

Note that we don’t even connect to DB anywhere, making this very fast. There is also no parsing/conversion. With the DB concept, you have to at least loop over the database rows. Using a normal config medium, such as ini, json or xml files would requiring some form of parsing after PHP loads. Whereas, with this method, it is a part of PHP’s loading process; you’re just including a small PHP file.