php id encoding to have exact same character length for any given id : <p>i want to encode id such as customer id to unique string (alpha/numeric) to hide the id, also i want to keep encoded string to have same length always, say 16 characters. Also it should be decodable.</p>

<p>example:
id = 1
encoded id = abcd12345e6f7g80</p>

<p>id = 100000
encoded id = edfgj129j5e6j3gk9</p>
