Live view and browser preview stopped working after switching from HTML to PHP

Live Preview is a waste of time.

Go to File ⇒ Open in Browser. 

Change your Preference settings to Default to Static Browser Preview.

When your local testing server & all processes are running, the default in your browser address bar should show

//:localhost/site-name/page.php 

If it doesn't, make sure your local testing server is properly defined in Site => Manage Sites.

Hope that helps.

@karls77727840 

Asked & answered in your other post below.  Please don't duplicate posts. It creates confusion.

https://community.adobe.com/t5/dreamweaver-discussions/browservorschau-funktioniert-seit-tahoe-26-0-1-nicht-mehr/td-p/15561135#M821

Browservorschau funktioniert nicht mehr
Ich habe das selbe Problem mit LIVE-View an einem MAC STUDIO.
Dreamweaver Version 21.6
Allerdings funktioniert es mit einem MAC BOOK mit derselben Dreamweaver Version 21.6
Hat jemand eine Idee?

i'm running mamp and i tried during DW and when DW has been closed

PHP is a pretext processor script. Do you have a testing server running? If no, then that could be causing your issue with live view as PHP pages need to be processed by a server so it gets turned into HTML to be displayed in the browser. If the server is not running, DW will be unable to find the dynamically related files and show content on the page such as QR codes, and browser previews will fail as well as it will look for the testing server that either does not exist or is offline.

What are you using for your testing server? Is it a remote server, and if so is that configured?

Or are you running a local server (ie: MAMP/WAMP) and is it running while you are building in DW?