PayPal\Auth\Oauth\OAuthSignatureMethodRsaSha1::check_signature PHP Method

    public function check_signature($request, $consumer, $token, $signature)
    {
        $decoded_sig = base64_decode($signature);
        $base_string = $request->get_signature_base_string();
        // Fetch the public key cert based on the request
        $cert = $this->fetch_public_cert($request);
        // Pull the public key ID from the certificate
        $publickeyid = openssl_get_publickey($cert);
        // Check the computed signature against the one passed in the query
        $ok = openssl_verify($base_string, $decoded_sig, $publickeyid);
        // Release the key resource
        openssl_free_key($publickeyid);
        return $ok == 1;
    }