Most web interactions are: your client sends a request to a server, the server sends back a response. That's kinda the model of php: single execution, no need to manage memory or resources because the world is destroyed once you've send your response. So php is a good fit for webdev.

Until you start playing with sockets or things like kafka then you really want languages which are made for long lived processes. But if you're just making a REST API, blog or anything which is not an app with sockets php is a good choice. Especially since 7.0, composer and the current leading frameworks Laravel and Symfony changed the landscape.