A lot of PHP work is digging around in Wordpress themes & plugins with a bunch of other (third-party) themes and plugins installed, some of them paid which can add another layer of annoyance to testing and deployment and such. Hosting's usually some managed thing rather than anything under your direct control, and usually quirky or limited in some way or another. It's a pretty miserable ecosystem to work in.
PHP itself is, secretly, actually kinda OK. Some major codebases written in it are no fun at all to work with, including the 800lb gorilla that is WP.
Combined with the JS work going on in WP, it's going to be an interesting 5 years I think. I would not be surprised if a lot of WordPress core starts to get rewritten. I know many of the large plugin authors are already pushing full steam ahead with modern PHP features and dropping support for old versions. Now that core can "take the blame" it's a lot easier to justify and I don't blame them.
PHP itself is, secretly, actually kinda OK. Some major codebases written in it are no fun at all to work with, including the 800lb gorilla that is WP.