android - Verifying in app billing response on server with PHP

Question

I'm trying to verify the response of the Play Store on my server. There are some questions about this topic but none have worked for me.

Here's how I'm doing it:

    $KEY_PREFIX = "-----BEGIN PUBLIC KEY-----\r\n";
    $KEY_SUFFIX = '-----END PUBLIC KEY-----';
$mykey=<MyPlayStoreKey>;
$key = $KEY_PREFIX . chunk_split($mykey, 64, "\r\n") . $KEY_SUFFIX;
$key = openssl_get_publickey($key);

    $correct=$param1=openssl_verify (
    $signedData, 
    base64_decode($signature),
    $key);

Where $signedData and $signature are responses from the Play Store. $correct is always 0 (Which means that the signatures don't match) What I'm doing wrong?

I'm testing this with static responses in a device with the developer account set as primary.