PHP cURL giving HTTP error 400, but in browser works fine

I’m trying to call a GET REST API, the problem is that the remote server gives me a HTTP 400 error. But when I put the link to my browser, it returns me the right response. It’s something wrong with my code?
The API I’m using is ArcGIS findAddressCandidates
Here’s the function i used:

function callAPI_GET($url) {
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    // Execute
    $result = curl_exec($curl);
    if ($result) {
        // Returns result
        return $result;
    } else {
        // Returns error
        return "Errore durante l'esecuzione della richiesta: " . curl_error($curl);
    }
}

Here’s the call:

$geo_request = callAPI_GET('https://geocode-api.arcgis.com/arcgis/rest/services/World/GeocodeServer/findAddressCandidates?city=' . $comune . '&SingleLine=' . $address_param . '&sourceCountry=ITA&maxLocations=1&f=json&outFields=location&token=*MY TOKEN*');