Lowest common denominator of web applications, widely known for it's poor programmers and many security problems.

I know many system administrators that do not allow PHP on their servers for just this reason.

OTOH it is very easy to build interactive sites with quickly, and it is a very easy language to learn.

Which explains why it is so popular and bug ridden.

The last time I audited a popular piece of PHP software for bugs I found an exploit within an hour, despite being unfamiliar with the software. (authors were notified on a public forum because they had no private contact details available).

To be fair most of the PHP applications are much more secure these days but the less well known add ons still stuffer from the same old stupid programming mistakes.