1 way encryption and 2 way encryption

what's the di开发者_StackOverflow中文版fference between 1 way encryption and 2 way encryption with php and MySQL?

One-way cannot be reversed. Two-way can be.

MD5 and SHA1 are examples of one-way "encryption" (hashing, really). AES_ENCRYPT is an example of two-way encryption.

PHP's crypt() function is also one way which is some what misleading because encryption generally means two way. But crypt effectively does the same thing as hashing (1 way), it just saves the salt with the output.