PHP cURL GET request and request's body

The accepted answer is wrong. GET requests can indeed contain a body. This is the solution implemented by WordPress, as an example:

curl_setopt( $ch, CURLOPT_CUSTOMREQUEST, 'GET' );
curl_setopt( $ch, CURLOPT_POSTFIELDS, $body );

EDIT: To clarify, the initial curl_setopt is necessary in this instance, because libcurl will default the HTTP method to POST when using CURLOPT_POSTFIELDS (see documentation).

CURLOPT_POSTFIELDS as the name suggests, is for the body (payload) of a POST request. For GET requests, the payload is part of the URL in the form of a query string.

In your case, you need to construct the URL with the arguments you need to send (if any), and remove the other options to cURL.

curl_setopt($ch, CURLOPT_URL, $this->service_url.'user/'.$id_user);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_HEADER, 0);

//$body = '{}';
//curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET"); 
//curl_setopt($ch, CURLOPT_POSTFIELDS,$body);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

  <?php
  $post = ['batch_id'=> "2"];
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL,'https://example.com/student_list.php');
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($post));
  $response = curl_exec($ch);
  $result = json_decode($response);
  curl_close($ch); // Close the connection
  $new=   $result->status;
  if( $new =="1")
  {
    echo "<script>alert('Student list')</script>";
  }
  else 
  {
    echo "<script>alert('Not Removed')</script>";
  }

  ?>