Jacob Santos makes some of his own comments about the recent PHP5 adoption talk that's been going around in the PHP community (spurred on by comments made by Matt of the Wordpress project).
Matt brings up some good points. What might be limiting PHP 5 adoption, could just be the lack of interest in developers. [...] Up until reading his rant, I've lived in a box where everyone I've talked to, used and enjoyed PHP 5 and its vast extensions. Developing in PHP 5.0 was uneventfully, but you learn to appreciate PHP 5 with the core inclusion of PDO with PHP 5.1. PHP 5 is not without annoyances. In the core developers attempts to "better" the language, they made changes that broke code that previously worked.
He looks at a few of the items for debate surrounding the move from PHP4 to PHP5 including the extensions that come bundled with PHP5, solving the register_globals issue, and a brief mention of the Standard PHP Library.
Our servers are running a version of RedHat enterprise, and are managed by a hosting company. Since installation was performed a long time ago, it is still using php4.
The developers are more than willing to move to php5, but everything on the server would need to be retested and fixed where necessary.
Unfortunately, it has been deemed that the cost of doing this would outweigh the benefits.
So, it's not always the developer who is to blame, but the penny watchers also have a say in it.