&reftitle.required; The driver requires PHP 5.5 or higher. The driver requires libbson and libmongoc, and will use bundled versions of both libraries by default. The driver requires OpenSSL and will rely on PHP to find its headers (i.e. PHP_SETUP_OPENSSL). If the build process fails to find OpenSSL, check that the OpenSSL development package (e.g. libssl-dev) and pkg-config are both installed. Cyrus SASL is an optional dependency and will be used if available.