debugger_on() undefined?

Greetings. I am running php 4.0.6, which I built as an apache module on Linux 2.2.14. I am trying to get debug information, using the 'debugger_on()' function. My compilation line (from phpinfo()) is: './configure' '--prefix=/usr/local/php' '--with-config-file-path=/etc' '--with-apxs=/usr/local/apache/bin/apxs' '--enable-track-vars' '--enable-magic-quotes' '--enable-debugger' '--with-mysql=/usr/local/mysql' '--with-interbase=/opt/interbase' However, when I execute a php script that includes the 'debugger_on()' function, I get: Fatal error: Call to undefined function: debugger_on() This would seem that although I said '--enable-debugger' in the configuration, my debugger is either: a) not working in php 4.0.6 or b) not compiled into my code. I appreciate any hints, suggestions, etc. The docs on php.net are rather weak on using the debugger_on() function. Thanks Jeff