How much revenue generation occurs on PHP? I'll cede the argument about the e-commerce platforms and CRMs, but I'm just not convinced that PHP is where a budding developer should be focusing their efforts. You enter the business/corporate world and there are tons of applications out there running the world, not just websites. Those applications are predominantly written in languages like .NET, Java, JS/ECMAScript, Python, Rust, and Go. Also, among the managed languages like .NET/Java/JS the knowledge is quite transferrable and sometimes almost identically named.
I'm not trying to bash PHP as a language, but every time I see this argument it's the same. Evangelizing PHP also seems to come with a requirement to mention Wordpress, Wikipedia, and Facebook. I'm sure there's money to be made in PHP, and I'm sure it's a great language for the internet. But learning .NET or Java is likely to have a much larger window of opportunity. Also, if you have a specific industry you want to work in you should be looking at the language predominately sought after in that industry.
I think this is why a lot of developers bash PHP, it's not that it's a non-valid choice. It's that it has limited applicability. I would never advise someone to learn PHP as their first language.