<?php

if (empty($_ENV['SLACK_CLIENT_SECRET']) || empty($_ENV['SLACK_CLIENT_ID'])) {
    die('Missing env. variables, abort!');
}

$provider = new Bramdevries\Oauth\Client\Provider\Slack([
    'clientId'          => $_ENV['SLACK_CLIENT_ID'],
    'clientSecret'      => $_ENV['SLACK_CLIENT_SECRET'],
    'redirectUri'       => 'https://slack-secret-santa.herokuapp.com/',
]);

if (!isset($_GET['code'])) {
    // If we don't have an authorization code then get one
    $authUrl = $provider->getAuthorizationUrl();
    $_SESSION['oauth2state'] = $provider->getState();
    header('Location: '.$authUrl);
    exit;

// Check given state against previously stored one to mitigate CSRF attack
} elseif (empty($_GET['state']) || ($_GET['state'] !== $_SESSION['oauth2state'])) {

    unset($_SESSION['oauth2state']);
    exit('Invalid state');

} else {

    // Try to get an access token (using the authorization code grant)
    $token = $provider->getAccessToken('authorization_code', [
        'code' => $_GET['code']
    ]);

    // Optional: Now you have a token you can look up a users profile data
    try {

        // We got an access token, let's now get the user's details
        $user = $provider->getResourceOwner($token);

        var_dump($token);

        // Use these details to create a new profile
        printf('Hello %s!', $user->getNickname());

    } catch (Exception $e) {

        // Failed to get user details
        exit('Oh dear...');
    }

    // Use this to interact with an API on the users behalf
    echo $token->getToken();
}

<?php

var_dump($_ENV);

--- 
+++ 
@@ -1,3 +1,52 @@
 <?php
 
-var_dump($_ENV);
+if (empty($_ENV['SLACK_CLIENT_SECRET']) || empty($_ENV['SLACK_CLIENT_ID'])) {
+    die('Missing env. variables, abort!');
+}
+
+$provider = new Bramdevries\Oauth\Client\Provider\Slack([
+    'clientId'          => $_ENV['SLACK_CLIENT_ID'],
+    'clientSecret'      => $_ENV['SLACK_CLIENT_SECRET'],
+    'redirectUri'       => 'https://slack-secret-santa.herokuapp.com/',
+]);
+
+if (!isset($_GET['code'])) {
+    // If we don't have an authorization code then get one
+    $authUrl = $provider->getAuthorizationUrl();
+    $_SESSION['oauth2state'] = $provider->getState();
+    header('Location: '.$authUrl);
+    exit;
+
+// Check given state against previously stored one to mitigate CSRF attack
+} elseif (empty($_GET['state']) || ($_GET['state'] !== $_SESSION['oauth2state'])) {
+
+    unset($_SESSION['oauth2state']);
+    exit('Invalid state');
+
+} else {
+
+    // Try to get an access token (using the authorization code grant)
+    $token = $provider->getAccessToken('authorization_code', [
+        'code' => $_GET['code']
+    ]);
+
+    // Optional: Now you have a token you can look up a users profile data
+    try {
+
+        // We got an access token, let's now get the user's details
+        $user = $provider->getResourceOwner($token);
+
+        var_dump($token);
+
+        // Use these details to create a new profile
+        printf('Hello %s!', $user->getNickname());
+
+    } catch (Exception $e) {
+
+        // Failed to get user details
+        exit('Oh dear...');
+    }
+
+    // Use this to interact with an API on the users behalf
+    echo $token->getToken();
+}
Add bootstrap code for slack oauth
