I have downloaded dbg for my version 4.3.10 version of PHP running on fedora 2.

The problem is after adding the extension and debug section to my php.ini, when I try to restart apache, it will not do so.

It doesn't give any error messages and none are in the logs.
Just no apache.

If anyone can help out I'd be very grateful.

It may not be caused by the debugger alone.
Apache logs its startup line before loading php extension and therefore even if dbg prevents apache from loading, you would see the line in the error log.
I'd recommend you check a) uid/gid access rights b) configuration settings.

Thanks for the reply. I have checked the error logs for apach and definitely no sign of an error.
When I restart apache using httpd -k restart, everything looks fine, and no error messages are displayed to the console either. But it just doesn't start. When I take out the extension and config options (which are exactly as documented)]all is well again. I just can't think what it might be.
BTW, what do you mean UID/GID
thanks

If you run apache under any account other than root, you have to make sure that this account has rights to load dbg.so.
Also, you may not just do gratefull restart to get php.ini changes in effect. You have to stop and start it.