It's not introspective enough compared to the other big dynamic languages, it suffers from a lot of low range developers working on it, the namespacing is a mess (which leads to to the docs although relatively thorough, but a mess). My understanding is that things like CakePHP are an improvement, but given PHP's underlying design a bit of a shim. Don't get me wrong people do interesting stuff with php (especially the pornographers), but it's a kludge. I also don't like the tendency for close binding of code with a real web server that I've observed.
Bear in mind my most recent PHP experience has been bending wordpress to do my will (taking over a project that's had the designer on the lead), and dealing with an undocumented not-quite-webdav implementation written in PhP that seemed to be overly dependent on apache.
Yeah should have said 'cake php or whatever' I don't know what the latest and greatest is, but I know cake was one of them not that long ago. But the PHP I've had to maintain recently has had most of the old problems of perl style CGI with the disadvantage of a lack of the extremely good toolchain that perl has.
And PHP's design flaws are at the core of the language without the extendability that perl has.
Bear in mind my most recent PHP experience has been bending wordpress to do my will (taking over a project that's had the designer on the lead), and dealing with an undocumented not-quite-webdav implementation written in PhP that seemed to be overly dependent on apache.