Cloud docs for Retry Strategy and PHP say "You cannot customize the default retry strategy used by the PHP client library."

https://cloud.google.com/storage/docs/retry-strategy#php_1

This is not accurate, the Cloud Storage client at least lets you supply a retries and requestTimeout parameter, which is worth noting:

$storage = new StorageClient(['retries' => 10]);

TODO: look into whether or not other retry configuration is available