Terms you need to know

Before we start looking at how encryption works in PHP, it is important that you understand a few pieces of encryption jargon:

Algorithm	The encryption method used to encrypt your data. Popular ones are TripleDES, Blowfish and Rijndael (now called AES)
Asymmetric encryption	This is encryption where different keys are used to encrypt and decrypt data. PHP does not support asymmetric encryption.
Ciphertext	The encrypted version of your source text
IV	Initialisation Vector - a seed for encryption and decryption. The IV used for encryption must match the one used for decryption. Your IV need not be kept secure, but it is generally best to keep it secure anyway.
Key	The secret encryption value used to encrypt your data. Combined with the IV, this forms your security - you should keep the key secret.
Plaintext	Your original source text, unencrypted
Symmetric encryption	This is encryption where the same key is used to encrypt your data as it is to decrypt it

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