I suppose my earlier comment wasn’t exactly expansive, so I may as well elaborate. I’m not reporting any news by saying that the uptake of PHP5 hasn’t been explosive – over the past year, most of the big names in PHP-land have been commenting on it on mailing lists and elsewhere. The figures weren’t leaving much wiggle room either – 80/20 splits in favour of PHP4 were approximately what we were seeing.
Thing is, while backwards compatibility is a good thing in general, in specific cases like this one – well, it’s not that it’s not a good thing, it’s that it’s not really applicable. PHP4 and PHP5 are enormously different beasties and treating one as a slightly enhanced version of the other isn’t really valid.
Hence, goPHP5.org, the new movement amongst the dev community to push for PHP4 to be dropped from applications and for 5.2 to be made a requirement. Lots of big names have signed onto this effort, including PHPUnit, Drupal, Solar, Symphony, Propel, phpMyAdmin, Typo3 and others. No shocker that Solar and Symphony would sign up I suppose – both being php5 frameworks from the get-go. However, the list continues to grow and with apps like Moodle leaning heavily towards signing up, this does look like it could run.
On the other side, however, the php internals developers are also pushing for a dropping of PHP4 – but this time from the language end, with no further support (other than serious security fixes) being provided and efforts being redirected to PHP5.2 and the upcoming PHP6.
Frankly, the sooner this happens, the better. 4 was always a half-finished idea, an OO language with half-implemented OO constructs. It served well when there was nothing else in place, but right now no developer in his right mind (and with a free choice in the matter) would use PHP4.