Php Encryptors

[phpsane]

Php Experts,

I know Md5 has been cracked and nowadays considered outdated. Otherwise, that was used for encrypting passwords.
Now, they use the hash. But from what I learn about the hash, you cannot decrypt it.
What I mean is, the Admin can never know what your real password is once it is saved in hashed format because the password cannot be de-hashed or decrypted.
I know all that stuff and so don't bother yourself explaining about it.

What I now want to do is create a Messenger where 2 members can communicate via encryption.
To do that, I need my system to decrypt each end user's messages. And so, which one to use ? 
Md5 is crap nowadays and has been cracked. 
If you were in my position then which encryptor (php) would you use to build your encrypted messenger with php ?

[requinix]

You of all people should not build this yourself. Or at all, in fact. But me saying that won't stop you.

This problem has been solved for years. Use the public-key encryption scheme. Google it.