Quite a few of the openssl functions require a key or a certificate parameter. Following methods may be used to get them:
Certificates
OpenSSL X.509) returned from openssl_x509_read()-----BEGIN CERTIFICATE-----Certificate Signing Requests (CSRs)
OpenSSL X.509 CSR) returned from openssl_csr_new()-----BEGIN CERTIFICATE REQUEST-----Public/Private Keys
OpenSSL key) returned from openssl_get_publickey() or openssl_get_privatekey()OpenSSL X.509)-----BEGIN PUBLIC KEY-----array($key, $passphrase) where $key represents a key specified using the file:// or textual content notation above, and $passphrase represents a string containing the passphrase for that private key