Can md5() be decoded?

[Immerse]

Question: does PHP have a native SHA-256 implementation or an implementation in an extension?

I've seen some scripts floating about, such as this one, but it's pretty processor intensive (although security is more important than waiting .25 seconds longer for a page to render).

[laurik]

This will guess weaker passwords:
http://bytez.net/utils/demd5.html