You could argue that PHP is slow as a language for a website, but looking at it differently you could also argue that it's blazingly fast. Here's how:

When a C, Java, Elixir, Go, Node.js, whatever site starts up, it may take a few seconds to a few minutes to initialize everything and start listening to incoming requests. It needs to setup a connection with the database, find and startup all plugins, check any configuration settings, etc. So this takes a while. Only then it can handle incoming requests and give users the web page content they asked for in their browser. It starts up once, then all requests are handled really fast by the running server, until months later it is stopped or restarted.

PHP does all this for every request! There is no running server. On every request, for every image in the page, for every javascript and css file included in the page, it does this whole startup sequence of contacting the database, initializing plugins, etc. Every time, as part of giving users their web page. So handling requests in PHP may be a bit slower, but since it's actually starting up a full server, its server startup time is super fast!

Yeah, I know, caching is essential and other caveats, but still...