Lukas Smith responds to some criticism that he and several of the other core PHP developer developers have gotten steadily over the years - "why don't you just rewrite PHP and get rid of all of the problems that have accumulated over the years?" His answer is, basically, "it would be a serious effort."
A lot of people have bet their business on PHP. They have invested heavily in building up large codes bases. More importantly a lot of people have bet their careers on PHP. So if we go an "reinvent" PHP from scratch, we would do these people a huge disservice. Even if these people would appreciate the rewrite as something they would have rather used, its too late for them. Too late for their current projects at any rate. I think its PHP.net's job to continue developing PHP to make sure it solves the "web problem" while ensuring a realistic upgrade path for its current users.
He supports any effort of a group that might come along and, taking the good in PHP, makes a new version and "reinvents" the language into something better, but he warns those groups that they should still be considerate of the past. Its his opinion that any group doing a major rewrite should work together with the current PHP developers, not as an opposing force. Knowing the history behind the language can only help others figure out where the true problems lie.
Also, be sure to check out the comments on the post for some other great opinions.