Laravel # Creating default object from empty value - php

Question

Trying to understand, why I'm not able to popup users balance using paypal sandox.
Here is my AccountBalance.php part code, when user paid in paypal
public function rebuildBalance($user_id, $amount, $bonus = 0, $frozen = false, $currency) {
$balance = UserBalance::where('user_id', $user_id)->where('currency_id', $currency)->first();
if ($bonus == 0) {
if ($frozen) {
$balance->balance_frozen += $amount;
} else {
$balance->balance += $amount;
}
} else {
$balance->bonus += $amount;
}
And when transaction is over, I got Creating default object from empty value
to this part $balance->balance += $amount;
Thankx

Answer 1

This is because your $balance variable is null from this query:
$balance = UserBalance::where('user_id', $user_id)->where('currency_id', $currency)->first();
Figure out why this query doesn't work the way you intend it to and you should be fine. A good start would be to figure out what $currency variable holds - and make sure you pass it correctly when calling rebuildBalance(args).
If you try to assign a property to null you get your exact error.