OAuth2\OAuth2::genAccessToken PHP Method

    protected function genAccessToken()
    {
        if (@file_exists('/dev/urandom')) {
            // Get 100 bytes of random data
            $randomData = file_get_contents('/dev/urandom', false, null, 0, 100);
        } elseif (function_exists('openssl_random_pseudo_bytes')) {
            // Get 100 bytes of pseudo-random data
            $bytes = openssl_random_pseudo_bytes(100, $strong);
            if (true === $strong && false !== $bytes) {
                $randomData = $bytes;
            }
        }
        // Last resort: mt_rand
        if (empty($randomData)) {
            // Get 108 bytes of (pseudo-random, insecure) data
            $randomData = mt_rand() . mt_rand() . mt_rand() . uniqid(mt_rand(), true) . microtime(true) . uniqid(mt_rand(), true);
        }
        return rtrim(strtr(base64_encode(hash('sha256', $randomData)), '+/', '-_'), '=');
    }