1. Low barrier to entry;
2. Hard to leak resources since the model is to tear down everything after a request finishes;
3. Stateless API core which means the efforts of creating an environment for a request for (2) is extremely low. Compare this to, say, the bootstrap time for Python or Java (which is why those generally don't follow the request teardown model);
4. Almost no multithreading.
This makes it great for servicing HTTP requests IMHO.
I need to compare it to Hack/HHVM though since I used that for years and it's still playing catch up with features Hack has had for years eg:
1. Hack has had the async-await model for years;
2. The type system is actually really good. It made me appreciate how nullability being part of the type system is incredibly useful. Plus it's had generics for years; and
3. Better inbuilt collection types with less odd coercion behaviour (ie dict, keyset, vec).
I find PHP hate in 2022 to be tired. Look at something like Laravel and PHP is completely fine. The sins of the past and even the odd inconsistencies still left in the language (eg needle and haystack param ordering) don't really matter.