API integration using PHP curl - php

Question

I am writing a script that does foreign exchange using an API to do it in realtime.
I presume that the problem is in my implementation of curl, as I get no output from this :
$currencyBase = "USD";
$currencyForeign = "EUR";
$url = 'https://www.alphavantage.co/query?function=CURRENCY_EXCHANGE_RATE&from_currency=' . $currencyBase . '&to_currency=' . $currencyForeign . '&apikey=KCUGBA9AP3Z1E2P8';
echo $currencyBase;
// create curl resource
$c = curl_init($url); //Initialize a cURL session
curl_setopt($c, CURLOPT_HEADER, 0); //Set an option for a cURL transfer
curl_setopt($c, CURLOPT_RETURNTRANSFER, 1); //Set an option for a cURL transfer
$this->fxRate = doubleval(curl_exec($c));
curl_close($c); //Close a cURL session
I have hardcoded
$currencyBase = "USD";
$currencyForeign = "EUR";
for debugging and I have also tried print_r($c) to see if I'm passing anything but I still get no output.
I know that my API call works because I have tried the link with entered USD and EUR and I get a response when I enter it in the browser as follows:
https://www.alphavantage.co/query?function=CURRENCY_EXCHANGE_RATE&from_currency=USD&to_currency=EUR&apikey=KCUGBA9AP3Z1E2P8
But I always get an empty response when I print the output from the script.

Answer 1

Your problem is this part of the code: $this->fxRate = doubleval(curl_exec($c));
curl_exec returns a string (which happens to be json), which you are casting to doubleval and that results in 0. Try it like this instead:
$this->fxRate = json_decode(curl_exec($c))->{"Realtime Currency Exchange Rate"}->{"5. Exchange Rate"};