Fix needed for PHP POST Curl to GraphQL ShopifyAPI

I am using PHP to communicate with the Shopify GraphQL API. Credentials are verified, test "read" calls work fine. Why is this code not working? I cannot for the life of me figure it out.



$url = 'https://'. $STORE_URL . '/admin/api/2020-07/graphql.json';

$curl = curl_init();
$queryData = array();
$data = array();

$queryData = 'mutation orderEditSetQuantity('.$OrderID.': ID!, '.$OrderLineItemID.': ID!, '.$newQuantity.': Int!) {
orderEditSetQuantity(id: '.$OrderID.', lineItemId: '.$OrderLineItemID.', quantity: '.$newQuantity.') {
calculatedLineItem {
id
}
calculatedOrder {
id
}
userErrors {
field
message
}
}
}';

$data["query"] = $queryData;

curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_POST, TRUE);
curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($data));
curl_setopt($curl, CURLOPT_HEADER, FALSE);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
'Content-Type: application/json',
'X-Shopify-Access-Token: ' .$SECRET
));

return curl_exec($curl);


I have tried everything, every combination of encoding/decoding, option toggles, even clunky manual string replaces, but CONSTANTLY I get this error returned:

{"errors":[{"message":"Parse error on \"26565467347\" (INT) at [1, 31]","locations":[{"line":1,"column":31}]}]}
What is going on?

$OrderID is an integer. There is no reason for it to even have double quotes around it. I figure this must be something to do with how the data is transmitted via POST so it is somehow decoded incorrectly on the other side.

If you have experience working with GraphQL, it is obviously preferred. Shopify API is maybe a bonus, but I THINK probably not required.

I think this is surely a very basic project, probably just a few lines of code will fix the issue, and my pricing will reflect that, I hope you consider that reasonable, I'll be watching this page like a hawk today because I really want to get moving on this thing so if anyone wants a quick, simple project for a modest payout - and you can genuinely help! Please do apply.