simple currency converter script using php - php

Question

I want to convert from dollars to Colombian pesos in PHP and that this is saved in a variable to use it in the paypal api, i have investigated and tested and I used this page https://free.currencyconverterapi.com/
Here's my code example:
<?php
function convertCurrency($amount, $from_currency, $to_currency)
{
$apikey = '*******';
$from_Currency = urlencode($from_currency);
$to_Currency = urlencode($to_currency);
$query = "{$from_Currency}_{$to_Currency}";
// URL para solicitar los datos
$json = file_get_contents("https://free.currconv.com/api/v7/convert?q={$query}&compact=ultra&apiKey={$apikey}");
$obj = json_decode($json, true);
$val = floatval($obj["$query"]);
$totalc = $val * $amount;
return number_format($totalc, 0, '', '');
}
//uncomment to test
echo "1 USD equivale a ";
echo convertCurrency(1, 'USD', 'COP');
echo " COP";
?>
but for some reason that i don't understand, the next day the server went down or something and now i have to use something else
Researching i also learned that google has an api but so many blogs that i have read it is not clear to me how to implement it, can someone please help me?
(I know that there are questions before this one with the same topic, but I feel that they are outdated...)