Google Slides Batch Update Errors - "Invalid JSON payload received. Unknown name" & " Cannot bind query parameter" - google-apis-explorer

Question

I'm trying to write to a slide element.
I keep getting the error responses of "Invalid JSON payload received. Unknown name" and " Cannot bind query parameter. Field"
My request is
{
"requests": [
{
"deleteText": {
"objectId": "g33c4ea3b90_0_9",
"textRange": {
"type": "FROM_START_INDEX",
"startIndex": 0
}
}
},
{
"insertText": {
"objectId": "g33c4ea3b90_0_9",
"text": "$8.23",
"insertionIndex": 0
}
}
]
}
I am posting to: https://slides.googleapis.com/v1/presentations/PRESENTATION_ID:batchUpdate?access_token=ACCESS_TOKEN
I am manually cURLing the request in PHP:
$params = '
{
"requests": [
{
"deleteText": {
"objectId": "'.$page_object_id.'",
"textRange": {
"type": "FROM_START_INDEX",
"startIndex": 0
}
}
},
{
"insertText": {
"objectId": "'.$page_object_id.'",
"text": "$8.23",
"insertionIndex": 0
}
}
]
}
';
$options = array(
CURLOPT_RETURNTRANSFER => true, // return web page
CURLOPT_HEADER => false, // don't return headers
CURLOPT_FOLLOWLOCATION => true, // follow redirects
CURLOPT_MAXREDIRS => 10, // stop after 10 redirects
CURLOPT_ENCODING => "", // handle compressed
CURLOPT_AUTOREFERER => true, // set referrer on redirect
CURLOPT_CONNECTTIMEOUT => 120, // time-out on connect
CURLOPT_TIMEOUT => 120, // time-out on response
CURLOPT_CUSTOMREQUEST => 'POST' ,
CURLOPT_SSL_VERIFYPEER => false,
CURLOPT_SSL_VERIFYHOST => false ,
CURLINFO_HEADER_OUT => true ,
CURLOPT_VERBOSE => true,
CURLOPT_POST => true,
CURLOPT_POSTFIELDS => $params
);
$ch = curl_init($url);
curl_setopt_array($ch, $options);
$content = curl_exec($ch);
curl_close($ch);
$obj = json_decode($content, true);
print_r( $obj );
When I call it from the API Explorer it works perfectly, but not from my server.

Answer 1

So the problem was the use of double quotes instead of single quotes in the request parameter json string.
So the following works:
{
'requests': [
{
'deleteText': {
'objectId': 'g33c4ea3b90_0_9',
'textRange': {
'type': 'FROM_START_INDEX',
'startIndex': 0
}
}
},
{
'insertText': {
'objectId': 'g33c4ea3b90_0_9',
'text': '$44.23',
'insertionIndex': 0
}
}
]
}
I had been working on this for two days.