Discord oauth2 example PHP

index.php

<?php
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
ini_set('max_execution_time', 300); //300 seconds = 5 minutes. In case if your CURL is slow and is loading too much (Can be IPv6 problem)
error_reporting(E_ALL);
define('OAUTH2_CLIENT_ID', 'PLEASE EDIT');
define('OAUTH2_CLIENT_SECRET', 'PLEASE EDIT');
$authorizeURL = 'https://discordapp.com/api/oauth2/authorize';
$tokenURL = 'https://discordapp.com/api/oauth2/token';
$apiURLBase = 'https://discordapp.com/api/users/@me';
$revokeURL = 'https://discordapp.com/api/oauth2/token/revoke';
session_start();

if(get('action') == 'login') {
  $params = array(
    'client_id' => OAUTH2_CLIENT_ID,
    'redirect_uri' => 'https://dev.keyinator.net/KeyBot/test.php',
    'response_type' => 'code',
    'scope' => 'identify guilds email'
  );
  // Redirect the user to Discord's authorization page
  header('Location: https://discordapp.com/api/oauth2/authorize' . '?' . http_build_query($params));
  die();
}
if(get('code')) {
    // Exchange the auth code for a token
    $token = apiRequest($tokenURL, array(
      "grant_type" => "authorization_code",
      'client_id' => OAUTH2_CLIENT_ID,
      'client_secret' => OAUTH2_CLIENT_SECRET,
      'redirect_uri' => 'https://dev.keyinator.net/KeyBot/test.php',
      'code' => get('code')
    ));
    $logout_token = $token->access_token;
    $_SESSION['access_token'] = $token->access_token;
    header('Location: ' . $_SERVER['PHP_SELF']);
  }
if(session('access_token')) {
  $user = apiRequest($apiURLBase);
  echo '<h3>Logged In</h3>';
  echo '<h4>Welcome, ' . $user->username . '</h4>';
  echo '<pre>';
    print_r($user);
  echo '</pre>';
  echo '<p><a href="?action=logout">Log Out</a></p>';
} else {
  echo '<h3>Not logged in</h3>';
  echo '<p><a href="?action=login">Log In</a></p>';
}
if(get('action') == 'logout') {
    apiRequest($revokeURL, array(
        'token' => session('access_token'),
        'client_id' => OAUTH2_CLIENT_ID,
        'client_secret' => OAUTH2_CLIENT_SECRET,
      ));
    unset($_SESSION['access_token']);
    header('Location: ' . $_SERVER['PHP_SELF']);
    die();
  }

function apiRequest($url, $post=FALSE, $headers=array()) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
    $response = curl_exec($ch);
    if($post)
      curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($post));
    $headers[] = 'Accept: application/json';
    if(session('access_token'))
      $headers[] = 'Authorization: Bearer ' . session('access_token');
    curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
    $response = curl_exec($ch);
    return json_decode($response);
  }
  function get($key, $default=NULL) {
    return array_key_exists($key, $_GET) ? $_GET[$key] : $default;
  }
  function session($key, $default=NULL) {
    return array_key_exists($key, $_SESSION) ? $_SESSION[$key] : $default;
  }
?>

Fixed logout with the tip of @crusardri

So if i implement it on a complete new page, say for example if i have a button on homepage to open another webpage consisting of an upload form, i want the upload page to be only limited to signed in discord user.. So if i just put this whole code in my upload.HTML file will it work? And what's the redirect URL thing in the code?

the API call itself is failing. Only reason this works is because you're removed the access token from session and refreshed the page.

that doesn't work, i will be directed to the main page not in discord to login when i test it.

Not working. Thank you =)

It works fine, only problem when I refresh the page while connected, it gives me an error