在某些情况下从 api 获取数据时获取 NULL

Question

我在通过 api 获取数据时遇到问题。当crypto ==“BTC”或“LTC”时，一切正常，但在其他情况下余额=NULL，你不知道它可能是什么？代码如下：

if ($krypto == "BTC") {
    $json = file_get_contents('https://api.blockcypher.com/v1/btc/main/addrs/1BSJxTKxu2RZfHCtEFpXShypn73Xmpry6N/balance');
}
elseif ($krypto == "LTC") {
    $json = file_get_contents('https://api.blockcypher.com/v1/ltc/main/addrs/LgzoEpUijQ39bWuY8XXQ2NUqrerebdE3w9/balance');
}
elseif ($krypto == "ETH") {
    $json = file_get_contents('https://api.blockcypher.com/v1/eth/main/addrs/0x7d8b9d28d373394fb23242eb838345f69c2ec25d/balance');
}
elseif ($krypto == "DASH") {
    $json = file_get_contents('https://api.blockcypher.com/v1/dash/main/addrs/XfUYFuyaca53cZHvJ9q679RqEo58wNRthp/balance');
}
elseif ($krypto == "DOGE") {
    $json = file_get_contents('https://api.blockcypher.com/v1/doge/main/addrs/DCrzwReRzPuaipX1ziQoTiLqotLD3sKMUz/balance');
}

$obj = json_decode($json);
$balance = $obj->balance / 100000000;