PHP's massive flaw is that it does one thing very well (web-dev), but does everything else rather poorly. It becomes the default choice for projects that start out as a web front-end, but then gets used in other situations where it's ill-suited. A lot of PHP projects have components that are hacked together and work, but are confusing and less-than-ideal from a design perspective.
Threading/asynchronicity comes to mind. I've worked on a few projects that started out as a web-front end, but then needed to do some background processing. Eventually the background process needs to be multi-threaded and the choices are: rewrite your code to support pthread's wrappers classes, use fork and shared memory segments, asynchronous web requests. All those solutions work, but they are much more complicated than the same task would be in most other languages with native threading support.
Threading/asynchronicity comes to mind. I've worked on a few projects that started out as a web-front end, but then needed to do some background processing. Eventually the background process needs to be multi-threaded and the choices are: rewrite your code to support pthread's wrappers classes, use fork and shared memory segments, asynchronous web requests. All those solutions work, but they are much more complicated than the same task would be in most other languages with native threading support.