我注意到的一件事是您正在将curl结果存储到变量中 $result . 这与查询结果所在的变量相同，因此替换它的值。那会引起麻烦的。
试试这个。

require 'init.php';
$body = $_POST['message'];
$title = $_POST['title'];
$url = $_POST['url'];

$path_to_fcm = 'https://fcm.googleapis.com/fcm/send';
$server_key = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxs";

$sql="SELECT * FROM fcm_info";
$result = mysqli_query($con, $sql);

$headers = array(

'Authorization:key=' . $server_key,
'Content-Type:application/json'

);

$message = array( 

  'title'     => $title,
  'body'      => $body,
  'webUrl'    => $url,
  'vibrate'   => 1,
  'sound'      => 1

 );

while($row = mysqli_fetch_array($result)){

 $fields = array( 

'to'        => $row[1],
'data'      => $message,
'priority'  =>'high'

 );

 $payload = json_encode($fields);

 $curl_session = curl_init();

 curl_setopt($curl_session, CURLOPT_URL, $path_to_fcm);
 curl_setopt($curl_session, CURLOPT_POST, true);
 curl_setopt($curl_session, CURLOPT_HTTPHEADER, $headers);
 curl_setopt($curl_session, CURLOPT_RETURNTRANSFER, true);
 curl_setopt($curl_session, CURLOPT_SSL_VERIFYPEER, false);
 curl_setopt($curl_session, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
 curl_setopt($curl_session, CURLOPT_POSTFIELDS, $payload);

 $curlResults[] = curl_exec($curl_session); //Changed the name of variable so it 
 //did not overwrite your query results.

 mysqli_close($con);

}