Something I pick on with PHP is because requests are so isolated, it doesn't have a good story for pooling SQL and HTTP connections. Its model really limits you when it comes to sharing resources between requests.
It's possible to have persistent MySQL connections, but there's all kinds of caveats; MySQL connections are stateful, so bad things can happen, and the performance benefits are only very slight. https://www.php.net/manual/en/features.persistent-connection...
This is indeed a downside but there are workarounds -- The wikimedia foundation put out a good blog post talking about getting HTTP connection pooling for PHP
