Ajax calls to php no longer synchronous

Not an AS issue directly but maybe someone here can help. I changed my website from php v5.6 to v8.2 and all my apps that relied on synchronous Ajax calls stopped working correctly. Naturally I reverted the site to v5.6 but the problem has not been resolved. No version of php will allow me to use synchronous Ajax calls, including ReadFile.
Obviously I can upgrade my apps to asynchronous ajax calls but…

  1. Are synchronous going to be depracated so should I modify my apps and move on?
  2. Anyone know a way of getting synchronous calls to work?

Synchronous and asynchronous requests

XMLHttpRequest supports both synchronous and asynchronous communications. In general, however, asynchronous requests should be preferred to synchronous requests for performance reasons.

Synchronous requests block the execution of code which causes “freezing” on the screen and an unresponsive user experience.