PHP cURL gives an error but works fine in POSTMAN

I have some problem(s) with PHP cURL. I tried to get data from the API using PHP cURL. This is my cURL code in PHP :

<?php

$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://www.example.com/dos/AW/API",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "{\"Filter\" : {\"IsActive\" : \"True\",\"OutputSelector\" : \"Name\"}}",
  CURLOPT_HTTPHEADER => array(
    "API_ACTION: GetItem",
    "API_KEY: MHlIARzQqxVpOg2dUxH4q9w7bx3pOL6K",
    "Accept: application/json"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

?>

With that code I can get a response but the response contains some errors. I also tried using POSTMAN to check, and the API works fine as I got a successful response with the same data. My question is: "Is there anything wrong with my cURL code that would explain why I got an error when I used cURL and I got successful response in POSTMAN "?

I would appreciate if someone could help me with this. Thank you very much.