RSA crypto functions

Hi I want to implement PHP functions using RSA part of OpenSSL which can encrypt, decrypt, sign and verify data. I do not, not yet at least, want to implement all the other OpenSSL stuff. I wouldn't mind but I should rather continue on other PHP stuff like the net- working code. Would it still make sense to put it in a new OpenSSL extension, so that others (or maybe I) can add more OpenSSL functions later on? Or would it be better with an RSA extension than in theory also can be implemented with other libraries by someone? Any other ideas on where they could go? Stig