In general, it is bad practice to touch transaction datasets in php script space. Like all foot-guns it leads to Read-modify-write bugs eventually.

Depending on the SQL engine, there are many PHP Cursor optimizations that save moving around large chunks of data.

Clean cached PHP can be fast for REST transactional data parsing, but it is also often used as a bodge language by amateurs. PHP is not slow by default or meant to run persistently (low memory use is nice), but it still gets a lot of justified criticism.

Erlang and Elixir are much better for clients/host budgets, but less intuitive than PHP =3