facebook/facebook-php-sdk — pull request #45 by favrik (2012-11-28 03:13:40+00:00)
Title: Use `empty()` for signed request value check

Use `!empty(...)` instead of `isset(...)` to check the signed request value inside the `getSignedRequest()` method. This avoids trying to parse an empty signed request, and removes the not very accurate "Unknown algorithm. Expected HMAC-SHA256." error from the logs. :)

See: http://stackoverflow.com/questions/13535474/unknown-algorithm-expected-hmac-sha256-error-due-to-signed-request-cookie-bein