如何用JSEncrypt对PHP中的数据进行解密

I'm trying to secure communication between a JS front-end and a PHP backend by using symmetric and asymmetric encryption. I'm creating a symmetric key on the client and encrypting it with the server's public key with JSEncrypt and sending it to the server for future use. However, I'm getting stuck when I get the data on the server side. openssl_open requires an envelope to decrypt the symmetric key and I'm not even positive what data is supposed to be in the envelope. I was under the impression that the envelope is the symmetric key that was encrypted with the public key, but using that has not worked. I've also tried different combinations of decoding as I've read that JSEncrypt encodes the message in base 64 and the key in hex, but those attempts are fruitless as well.I'm trying to secure communication between a JS