PHP client post request to Server side and server side post request to remote server

My scenario is as follows:

1. when button clicked, client side will post request to server side
2. once server side receive the request, it will post another request to remote sever to get the result
3. once the response comes, server side should echo the response to client.

client

$.post('login_server.php'{act:"post",phone:phone,passwords:passwords},function(e){
      alert(e);
    },'json');
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server

$act = isset($_POST["act"]) ? $_POST["act"] : "default";
if($act == "default"){
    var_dump(123123);
}elseif($act == "post"){
    $phone = $_POST["phone"];
    $password = md5($_POST["passwords"]);
    $data_array = array('phone' => $phone,'password' =>$password );
    $jsonStr = json_encode($data_array);
    $url = "http://xx.xx.xx.xx/xxxx/userinfo/login";
    $data = http_post_json($url, $jsonStr); 
    echo json_encode(123);  
}

function http_post_json($url, $jsonStr)
{
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonStr);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array(
                      'Content-Type: application/json; charset=utf-8',
                      'Content-Length: ' . strlen($jsonStr)
                )
            );
  $response = curl_exec($ch);
  $abc = json_encode($response);
  $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  return array($httpCode, $response);
}
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I checked the login_server. It can get the response from remote server. But if I add

$response = curl_exec($ch);Copy code

the callback function doesn't work.

Is there anyone know this?

BRs Damon