If I set a breakpoint and debug without checking "Run in External Browser" in the IDE settings, everything works fine, i.e., it stops at the breakpoint. But if I check that box, then I do get a separate browser window, but the code doesn't stop at the breakpoint as I expected it to.

Am I misunderstanding what this setting is supposed to do?

please read this http://forum.nusphere.com/howto-run-debug-session-t585.html first.
If you open new browser window, dbg cookie is not passed to it (it's the way the browser should work) and therefore you'd take care of supplying/passing DBGSESSID.

Sorry, but this still eludes me.

I tried adding a RUN parameter for DBGSESSID with value 1;d=1,p=0, but got:

Using 1@client;d=1,p=0 didn't help either.

I then removed the parameter and added a DebugBreak() call in my code. No error message, but it never stopped at the breakpoint.

Then I remembered I was using SSH, so I tried the parameter again with 1@localhost;d=1,p=0 but then it never stopped at the breakpoint.

Everything else seems to be fine, since when I uncheck "Run in external browser" it works.

it means that either 192.168.1.1 is not in the list of allowed hosts or port 7869 is not in the list of allowed ports.

Sorry, I meant to say that the "not allowed" error did go away once I specified localhost in the value of DBGSESSID. However, although there are now no error messages, and I am specifying DBGSESSID as a RUN parameter, the external browser still doesn't stop at the break point, whether I insert it in the IDE or add a DebugBreak() call.

Well. What happens then ? You get a blank screen, HTTP/404 or what ?

Nothing strange happens at all. The program simply runs normally as though there were no breakpoint at all.

ok. Put phpinfo(); die(); as the first line of the script then run it as you did and send me the results.
TIA.

I can't run it again and send the results because now I'm getting:

Please see my posting in
seems-there-is-no-default-html-browser-installed-t527.html