The former PHP developer has no idea what has PHP become since version 7. Most of these points about PHP 7+ (Especially PHP 8) are invalid. Moreover, you must consider rewriting the entire article with more context and do a bit of research.
1. Maintenance of PHP backend is as smooth as cheese when you use powerful frameworks like Symfony and Laravel.
2. PHP has vastly improved performance since version 7.4+. In fact, PHP performs faster and handles more requests when compared to Node JS and Python.
Extending PHP with Swoole or RoadRunner gives performance comparative to GoLang.
3. For every framework except may be some WASM based (eg. Blazor), frontend is always best handled by JavaScript. And again, you need to describe why PHP is not best for pure server-side, even after a lot of performance and security improvements, strict type systems, and awesome (highly maintained, easily manageable and scalable) frameworks.
4. Being a DIY and being easily accessible to the beginners isn't a problem, unless it can pose security risk or make the code unmaintainable. But this isn't a concern if you follow the best practices.
5. Compatibility issues affect only a few lines of code, which again happens when most languages/frameworks perform the major upgrades. But why does it pose security problems? 🤔
6. I've never seen HTML syntax inside PHP except < ? php tag, which was never an issue. And I think you (or the developer that told you) have never used headless development (separate server-side/client-side development) and therefore have no idea about how those things work.
7. Again, you have no idea how coupled/decoupled programming works, if you use coupled framework, you need to mix HTML with backend regardless of whether it is JavaScript, Java, or Python. If you use headless (API based framework), you won't see any HTML inside the code.
P.S.
1. You must provide additional context while writing something like this.
2. You must do a prior research or know more about the language before judging it.
3. You cannot judge a language/framework by its history.
