Stripe API create SKU - php

Question

I need to create a SKU via stripe API.
The problem is in inventory field.
Stripe api response is:
'error' => [
'message' => 'Invalid hash',
'param' => 'inventory',
'type' => 'invalid_request_error'
]
My php code is:
$endPoint = 'https://api.stripe.com/v1/skus';
$APIKEY_TEST = 'my_api_key';
$headers = array('Authorization: Bearer '.$APIKEY_TEST);
$sku = [
'active' => 'true',
'inventory' => ['quantity' => 10000000 ,'type' => 'infinite', 'value' => null],
"currency" => "eur",
"price" => $price,
"product" => $stripe_product_id
];
$array_string ='';
foreach($sku as $key => $value) {
$array_string .= $key.'='.$value.'&';
}
rtrim($array_string, '&');
$ch = curl_init();
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_URL, $endPoint);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $array_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
$output = curl_exec($ch);
curl_close($ch);
In stripe api docs inventory is hash type field.
I have tried json_encode() without luck.
Maybe the problem is in sending an array instead of a hash.
In $sku array, inventory field is also an nested associative array.
Maybe the problem resides there as well.
Is there a way to send CURLOPT_POSTFIELDS containing inventory so that stripe accepts it?
EDIT:
In Stripe dashboard i can see my request:
{
"active": "true",
"inventory": "Array",
"currency": "eur",
"price": "3",
"product": "prod_F6ipvfYFvOxxQq"
}
Inventory field has no data, but instead "Array".

Answer 1

After trying a lot of possible solutions, i found the answer:
$post_array = http_build_query($sku);
And know stripe accepts the $sku array with nested inventory array.
It worth notice that stripe does not accept JSON in requests.
The request has to be url encoded.