"With PHP 5 offering a viable upgrade path for the last
few years, the recommendation is for addministrators and developers
is to move to the PHP 5 platform (if they haven't already done so),
which is currently at 5.2.6. PHP 4 developers that have not
previously been introduced to PHP 5 may find that some code will
need to be refactored, but a well-designed application will need
fairly minimal tinkering to function with the new
version."