openssl_get_publickey返回“资源ID＃2”

Question

I am doing the In-App Purchase verification server side for android. My PHP Version is 5.6.28, and my OpenSSL version is 1.0.2j .

I am having problems with getting the public key. The code below returns Resource id #2:

$key = openssl_get_publickey( $publicKey );

My public key is created from :

"-----BEGIN PUBLIC KEY-----
" . chunk_split($base64EncodedPublicKeyFromGoogle, 64, "
") .  "-----END PUBLIC KEY-----";

where base64EncodedPublicKeyFromGoogle is the public key from google

I tried searching what "Resource id #2" means but cant find any. Any one knows what this means and how to make openssl_get_publickey work?