Question

I have a site in multiple languages. I have a method that returns me the today currencies in a array. I display that currencies in a table then.

// --- en/index.php
<?php
include_once "../exchangeRates.php";
$currencies = ReadExchangeRates();

// --- fr/index.php
<?php
include_once "../exchangeRates.php";
$currencies = ReadExchangeRates();

...
// somewhere in the page
<td><?php echo $currencies["eur"]["today"]; ?></td>

So, every time I load, en/ or fr/ or other language, I request the exchange rates from a external site.

Can I optimize this behavior (reading once per day or session)?

maybe to store a global variable and check the update date?

Answer 1

All variables die with the script, global or local, they can’t be used for cache purposes.

You have several solutions depending on your resources:

• You can pick the exchange rates, serialize them as a string and store it into a file. When you you need to print them, read the file modification time; if it’s older than X, fetch fresh data from the external server, otherwise unserialize your current data and display it.

• And, of course, you can simply store raw data in a proper SQL database and update it in regular basis.