Another follow up on this:
PHP is easy. That means you will have many people making use of it. Non-coders and coders alike. It is easy for non-engineers and non-CS majors to grasp and start using.
Another thing going for it: Wordpress.
Tonnes of themes, plugins, etc. Wordpress is easy. Widely used. VERY functional.
I've been looking for a way to move way from Wordpress and PHP to say Python. No go. Nothing approaches the ease of use and feature sets. Sure, I can roll my own. Start with Django or go lower level with Twisted. But then it becomes a support nightmare for long term maintenance of themes, plugins, core code, etc.
PHP has flaws. But then again, every programming language has flaws. And in many cases, the flaws depend on who you ask, the usage case, etc.
But in terms of survivability of a language, PHP rocks where it counts. IE, widespread usage, plenty of documentation, an AWESOME online web search at php.net, and without much technical knowledge you can make use of the language. Language survivability isn't the same as language elegance.
In that context, a cockroach, rat, cats, etc. might be a better image to represent what PHP is: a hardy language that refuses to go away.