Well, you should school those fools at Google, Facebook, Twitter, Pinterest, Amazon... and tell them how they are wasting time with their toy MySQL databases.
> those fools at Google, Facebook, Twitter, Pinterest, Amazon
... have dedicated hundreds of engineers and millions of dollars to nothing more than keeping MySQL up, running, and not crapping the bed every time someone looks at it funny. If you can afford that resource expenditure, by all means go nuts with MySQL. Most companies can't and would be far better served by something which doesn't need that amount of handholding to serve its basic purpose.
There is one thing that bugs me about all the talk of postgres' superiority: why haven't these companies switched to postgresql? Surely they weren't all too far invested in mysql before a "more knowledgeable" DBA came along saying postgresql is better.
Following on from that, I suspect a lot of large companies use MySQL because they always have, not because it's actually any good. For example, Basecamp used MySQL while I was there, but I never met a single Sysadmin there who would use it over Postgres if they were to start a new project.
PHP was built for the web and has been successful at that job. It is easy to use because the core developers have made some good design choices for the task at hand. For example no threads, stateless requests, core functionality focused on outputting HTML, etc.
MySql and PHP are good. They do the job they were designed for in a cost effective way and of course that means there will be trade offs.
PHP is crap. It's actively hard to write good code in it. Not good code like SOLID or pretty code that's self documenting, it's hard to write code that's not going to break in unique and interesting ways.
Sure, you can knock up a contact form in it really quickly, but that ease of use hides significant dangers.
This might have been true 10 years ago with versions like PHP 4. But remember many companies have invested a lot into PHP including Facebook. In the newest version of PHP what you said cannot apply with a type system, OOP features like traits, class inheritance etc.
> Surely they weren't all too far invested in mysql
I think by the time Postgres sorted itself out into a more user/admin-friendly system (which is still fairly recently, really), MySQL had pretty much conquered the "quick and easy" mindshare and was deeply embedded almost everywhere.
And if you've spent millions of dollars architecting your systems such that MySQL's flaws aren't killer issues, there's very little financial benefit to switching, I guess.
MySQL for years was far easier to install, configure and run than PostgreSQL, especially features like replication which was much better than other options. Big companies use these databases as more like simple key/value systems rather than complex relational schemas so strong replication and operational simplicity was favored over the rich featureset of Postgres.
Eventually Postgres caught up in most things, and the delay was in some part because of implementing those features "correctly" and with more thought, but it's still a delay that hurt the uptake in the early days.
