How do I encode something in PHP with a key?

I see base64_encode can encode values, but without a key. I need a function that takes a salt and data, encodes it, and can be decoded with the same salt (but if you try to decode it without the salt, it 开发者_StackOverflowgives you gibberish).

Is there a PHP function for this (can't find it, only modified versions of base64_encode).

EDIT: Found the answer: use mcrypt ciphers

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What about taking a look at http://www.php.net/manual/en/book.mcrypt.php