Apparently, it isn't PostgreSQL; If you have no need for Postgres features and you're not familiar with it, sticking to MySQL is fine.
It is not a matter of what you need, it is a matter of using good tools that will help you do good work, understand better what you do, build durable products, and so on.
Just one example: MySQL will not complain if you add a check constraint but will not actually add it to your schema. That's a very Microsoft-y way to handle things, and should give cold sweat to any coder.
I believe it was left to support certain migrations(?). You can create a trigger instead.
I'm pretty certain many people will consider MySQL a good tool with which they produce good work. While it may have its quirks, it's present on virtually all shared hosting environments, just like PHP, so it's very easy to create and deploy an application powered by both these technologies.
I have hard time to believe you are serious here...
I'm not saying this MySQL behavior is acceptable, I'm just saying that you should be aware of the limitations and quirks of the tools you work with.
I think the bad reputation still sticks to it.
There are enough troubles with SQL (eg the Null debate) to add up to the mess by adding guesses.