public readonly variables

I know the subject line might sound a bit like an oxymoron, but bear with me! What I'd like to have is a property of an object that behaves like a public variable when it comes to reading, but like a protected one when it comes to writing, as it would make my code a lot easier to read. I know about the __get($var) method to magically provide this behaviour, but from all I've read it can be pretty slow compared to a regular public variable. I've seen a thread on the dev lists where someone requested it, but can't find anything in the manual. Does anyone know if this is available in a later version of PHP, or if it's implementation is penned for some time in the future? Thanks, Ash http://www.ashleysheridan.co.uk