Extract access token from the php linked callback value of Nearo (login with Naver ID)

Naver Login Access Token Acquisition Example consists of two files. (naverlogin.php, callback.php)
1. naverlogin.php
<?php
  // Naver Login Access Token Request Example
  $client_id = "YOUR_CLIENT_ID";
  $redirectURI = urlencode("YOUR_CALLBACK_URL");
  $state = "RAMDOM_STATE";
  $apiURL = "https://nid.naver.com/oauth2.0/authorize?response_type=code&client_id=".$client_id."&redirect_uri=".$redirectURI."&state=".$state;
?><a href="<?php echo $apiURL ?>"><img height="50" src="http://static.nid.naver.com/oauth/small_g_in.PNG"/></a>

2. callback.php
<?php
  // Naver Login Callback Example
  $client_id = "YOUR_CLIENT_ID";
  $client_secret = "YOUR_CLIENT_SECRET";
  $code = $_GET["code"];;
  $state = $_GET["state"];;
  $redirectURI = urlencode("YOUR_CALLBACK_URL");
  $url = "https://nid.naver.com/oauth2.0/token?grant_type=authorization_code&client_id=".$client_id."&client_secret=".$client_secret."&redirect_uri=".$redirectURI."&code=".$code."&state=".$state;
  $is_post = false;
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_POST, $is_post);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  $headers = array();
  $response = curl_exec ($ch);
  $status_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  echo "status_code:".$status_code."
";
  curl_close ($ch);
  if($status_code == 200) {
    echo $response;
  } } else {
    echo "Error Content:"$response;
  }
?>

// Naver API Example - Member profile inquiry
<?php
  $token = "YOUR_ACCESS_TOKEN";
  $header = "Bearer".$token; // Add space after Bearer
  $url = "https://openapi.naver.com/v1/nid/me";
  $is_post = false;
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_POST, $is_post);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
  $headers = array();
  $headers[] = "Authorization: ".$header;
  curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
  $response = curl_exec ($ch);
  $status_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  echo "status_code:".$status_code."<br>";
  curl_close ($ch);
  if($status_code == 200) {
    echo $response;
  } } else {
    echo "Error Content:"$response;
  }
?>