Duh. Didn't realize the Output window was used by PHP Tools.
When I first click on a link (on any page), the following three lines appear:
Accepting connection from Xdebug.
Sending the socket to Visual Studio (port 49603)
Auto-attach to process '[38300] php_remote.exe' on machine 'xxxxx-xxxx' succeeded.
The debugger basically hangs (spinning hourglass in Visual Studio) at that point. I've waited 5 minutes to see if it times out--it doesn't.
When I click the link a second time, the following lines appear. Note that the two "click" events both appear after the second click:
click
click
[Sun Jul 25 15:57:54 2021] ::1:58313 [200]: /nonprofit.php?id=139
Accepting connection from Xdebug.
Sending the socket to Visual Studio (port 49603)
Auto-attach to process '[26184] php_remote.exe' on machine 'xxxxx-xx' succeeded.
The program '[38300] php_remote.exe' has exited with code -1 (0xffffffff).
[Sun Jul 25 15:57:58 2021] ::1:63223 [200]: /nonprofit.php?id=139`
Thanks.