It would be useful if you had some idea of who your public is. Then you could place some (hopefully unobtrusive) affiliate links for some product/service of their interest.
Fair enough. I've been trying to think of a good way to do present it — you really need to see the full screen to get how subtle and delightful the effect can be. I am still iterating; thanks for the vote towards a video.
Security holes, or just bad practices in general.
My biggest gripe with PHP is that every CMS, framework, custom built site uses a different style, some echo HTML some even output HTML in the middle of a class definition etc.
I remember reading popular Joomla! extension that counted the number of elements in a one dimensional array with a for loop.
They are just the language of the year, this year it will probably be all about go and node.js and maybe next year it will be about Steve's Language and ASP.
Moral of the story is, it's just whats in season this year. Some people will argue better languages, but really there are problems with all of them.
If you want to do freelance work, learning PHP (or ASP) is mandatory. Sure, Ruby is great, but you'll keep stumbling on :
"our shared host is PHP only, we don't want to change for another"
"we want wordpress"
"our computer guys know a little PHP, we need PHP"
"what the fuck is Ruby ?"
So you'll try to educate your client, to explain why Ruby us great. But you'll fail, because most clients don't give a shit and, for their very basic needs, PHP is as good as ruby.
I think it makes sense to learn PHP. The only money i'm making right now is javascript (working on Business Catalyst sites) and Wordpress (custom themes and plugins.) Many decent self-described programmers would consider it shitwork, and they'd probably be right... But there's a lot more PHP work out there right now than there is Python or Rails.