PHP's greatest strength is that it doesn't require OO. Seriously, for most simple web application tasks (and even some complicated ones) OO adds more confusion than it removes, and I say this as someone who certainly sees the value in OO for complex apps.

Most web apps are ultimately more like shell scripts or console applications than desktop/mobile applications. It's no coincidence that most of the former are written in C or C-like scripting languages, and most of the latter are written in OO languages running on .NET or Java. Your basic operations are "print some stuff", "read from a file or database" and various sorting, slicing and text-processing tasks inbetween, all of which are done well by PHP, Perl, C and so forth. ActiveRecord, TableDataGateway etc. are great patterns for data access, but sometimes mysql_query("SELECT foo FROM bar WHERE x = y") is just so much simpler that it becomes the better option.

The lack of OO makes PHP's documentation much more browseable, and makes code more readable in certain situations. If I look at your code and I see a function I don't know, I just google it. If I see a method invocation on an object, I need to figure out the type of the object (not easy in a dynamic language) and google the combination of class and method name, which often fails to return a result (has anyone ever managed to find anything useful in the Zend Framework docs?). PHP isn't the only data point for this argument - I think it's probably why Drupal handily beats ZF, Symfony etc. in terms of popularity, despite the superior OO architecture of the latter. You can google pretty much any API function and get an accurate result, which you just can't do with ZF (which lacks documentation at the method level, and what documentation that exists is buried in some Doxygen-based site which is made impervious to search by the use of frames). I'm also reminded of Linus's argument against OO in the Linux kernel - when you're all about the patch files, you need clear function names to understand what's going on without massive amounts of context. Drupal's rate of contributions probably exceeds that of other frameworks for similar reasons.

Of course, this bias against OO is also what makes PHP a bad choice for certain things, and this is why plenty of devs hate it. I honestly don't know if, in the final analysis, this makes PHP a good or bad choice. It probably depends too much on the problem you're trying to solve for there to be a simple answer.