如何向我当前的 Facebook 应用程序用户请求额外许可？

Question

我正在使用此代码向用户请求我的应用程序的许可，

 $app_id = "1231654321654121";
 $canvas_page = "http://apps.facebook.com/manydldotnet/";
 $auth_url = "https://www.facebook.com/dialog/oauth?client_id=" . $app_id . "&redirect_uri=" . urlencode($canvas_page) . "&scope=email,read_stream";

 $signed_request = $_REQUEST["signed_request"];

 list($encoded_sig, $payload) = explode('.', $signed_request, 2); 

 $data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);

 if (empty($data["user_id"])) {
        echo("<script> top.location.href='" . $auth_url . "'</script>");
 }

但现在我需要向当前用户请求“publish_stream”权限， 我向范围参数添加了“publish_stream”权限，但对于之前已经授予应用程序权限的用户来说，它不起作用。

那么我该如何解决这个问题呢？

谢谢...

Answer 1

显然，一旦用户授权您的应用，user_id 将始终出现在 signed_request 中。因此，您需要检索用户的权限并进行检查。

这是一个示例：

<?php
$app_id = "APP_ID";
$app_secret = "APP_SECRET";
$canvas_page = "http://apps.facebook.com/appnamespace/";
$GRAPH_URL = "https://graph.facebook.com/";
$scope = "publish_stream,email";
$auth_url = "https://www.facebook.com/dialog/oauth?client_id=" . $app_id . "&redirect_uri=" . urlencode($canvas_page) . "&scope=" . $scope;

$signed_request = $_REQUEST["signed_request"];

$data = parse_signed_request($_REQUEST["signed_request"], $app_secret);

if (empty($data["user_id"])) {
    echo("<script> top.location.href='" . $auth_url . "'</script>");
    exit;
}

$permissions = json_decode(file_get_contents($GRAPH_URL . "me/permissions?access_token=" . $data["oauth_token"]), TRUE);
if( array_key_exists('publish_stream', $permissions['data'][0]) ) {
    // Permission is granted!
    // Do the related task
    echo "You granted the publish_stream permission to my app!";
} else {
    // We don't have the permission
    // Alert the user or ask for the permission!
    echo("<script> top.location.href='" . $auth_url . "'</script>");
}
function parse_signed_request($signed_request, $secret) {
    list($encoded_sig, $payload) = explode('.', $signed_request, 2);

    // decode the data
    $sig = base64_url_decode($encoded_sig);
    $data = json_decode(base64_url_decode($payload), true);

    if (strtoupper($data['algorithm']) !== 'HMAC-SHA256') {
        error_log('Unknown algorithm. Expected HMAC-SHA256');
        return null;
    }

    // check sig
    $expected_sig = hash_hmac('sha256', $payload, $secret, $raw = true);
    if ($sig !== $expected_sig) {
        error_log('Bad Signed JSON signature!');
        return null;
    }

    return $data;
}

function base64_url_decode($input) {
    return base64_decode(strtr($input, '-_', '+/'));
}
?>

更多内容可以在我的教程中找到：如何：检查用户是否具有特定权限 – Facebook API

Answer 2

我非常确定，一旦您将请求的新权限添加到您的范围，Facebook 将自动通过应用程序的请求访问对话框再次提示它们，并且用户只需批准它们即可。

Answer 3

<fb:login-button scope="create_event">Grant Permissions to create events</fb:login-button>