I discovered plenty of website hosts are reluctant to upgrade to PHP5.3. Many of them provided this is because you will find plenty of bugs in PHP5.3, so that they would rather ensure that it stays at version 5.2.
What's wrong with v5.3 then? is the fact that true the things they stated - plenty of bugs? I've not run into any bugs on my small local server! Or could they be just reluctant to upgrade!??
- IIRC the bytecode caches weren't ready and modified for that new ABIs and Zend_core changes when the initial PHP 5.3. was launched. That's meanwhile solved, however the suspicion stays.
- Then there's too couple of user demands really, since not a great deal of code is dependent on 5.3 features yet.
- A couple of compatibility breaks exist (there have been some Wordpress and Drupal issues, but the majority of the issues are exaggerated).
And thus most shared hosters don't have any incentive to upgrade existing servers.
They are just reluctant to upgrade because of maintanence costs. This is also true for hosting that is shared companies.
Without a doubt isn't the only reason, but this (little) change has produced lots of problems in Content management systems like drupal:
Note: There's no reference sign up a function call - only on function definitions. Function definitions alone are sufficient to properly pass the argument by reference. By PHP 5.3., you're going to get an alert stating that "call-time pass-by-reference" is deprecated if you use &lifier in foo(&lifier$a).
Cited from PHP: Passing by Reference
So, most likely the very first website hosts moving to php 5.3 have been flooded by support demands originating from little (and unexperienced) web managers.
Hence, I guess others made the decision to wait for more stable situation...