If the extension is compiled against a version of PHP without OpenSSL, the functions in src/contrib/php-ssl.h will not be declared (they are wrapped in an #ifdef HAVE_OPENSSL_EXT block); however, php_phongo_ssl_verify() still attempts to call these functions, which results in missing symbol errors.

We should check #ifdef HAVE_OPENSSL_EXT again from php_phongo_ssl_verify() and report an error to the user:

Cannot verify certificate expiration. Please ensure that extension is compiled against PHP with OpenSSL or disable the "verify_expiry" SSL context option.

php_phongo_peer_verify() also needs a similar check for the built-in host name verification on PHP versions before 5.6:

Cannot verify remote certificate SubjectAltName or CN. Please ensure that extension is compiled against PHP with OpenSSL or disable the "verify_peer_name" SSL context option.