title: libsodium PHP storing private key in file
body: <p>I have been using the openssl libraries in PHP to generate keypairs for RSA encryption, and have seen that in the latest version of PHP, 7.2, libsodium has now been integrated.</p>
  
  <p>I would like to update to the newer library, and can generate the keypairs. In the openssl libraries I was able to export the keys to an encrypted keyfile, for storage on the filesystem.</p>
  
  <p>How is this equivalence achieved with libsodium?</p>
  
  <p>Thanks,</p>
  
  <p>Leon</p>