Note that OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING were introduced by this commit:
https://github.com/php/php-src/commit/9e7ae3b2d0e942b816e3836025456544d6288ac3
Before that, the options arg was called raw_output and was a Boolean so if you're considering this method as a replacement for mcrypt_encrypt(), this will only work with PHP 5.5 and above.
A good guide on replacing Mcrypt encryption/decryption methods with the OpenSSL parallels can be found here:
http://thefsb.tumblr.com/post/110749271235/using-opensslendecrypt-in-php-instead-of