How to make PHP 5.2 compatible with future versions

Question

I am writing a CMS in version 5.2 but I am worried whether or not it will be compatible with PHP 5.3 or future versions for that matter.

What things I should watch out for or there is nothing to worry about ?

P.S: Please don't suggest that I should use PHP 5.3 instead as that's not the question asked.

Answer 1

PHP takes a very conservative approach to backwards compatibility. Most code will continue to work for quite a while - I've seen PHP3 code that's still OK in 5.3.

You should keep an eye on the lists of backwards incompatible changes.

Answer 2

You should check the list of backwards incompatible changes here: http://www.php.net/manual/en/migration53.incompatible.php

Answer 3

One thing that I currently have encountered and in some ways is pretty serious is that php > 5.3 no longer supports natively mssql (Microsoft SQL server) extension. I don't know if that is of any good use to you. But from 5.3 version php dropped support for it and suggests that you use Microsofts' extension instead: http://www.microsoft.com/download/en/details.aspx?id=20098