When I try to compile dbg on SUSE 9.3 x86_64, I get lots of errors. So I want to ask if it is possible to compile dbg for the x86_64 architecture, at all?

I downloaded the "DBG 2.11.32 module sources" and extracted them to /usr/local/src/dbg. When running ./deferphpize I get the following output:

spacejet:/usr/local/src/dbg # ./deferphpize
Configuring for:
PHP Api Version: 20031224
Zend Module Api No: 20041030
Zend Extension Api No: 220040412
configure.in:9: warning: underquoted definition of PHP_WITH_PHP_CONFIG
run info '(automake)Extending aclocal'
or see http://sources.redhat.com/automake/automake.html#Extending-aclocal
....
gcc -I. -I/usr/local/src/dbg -DPHP_ATOM_INC -I/usr/local/src/dbg/include -I/usr/local/src/dbg/main -I/usr/local/src/dbg -I/usr/include/php -I/usr/include/php/main -I/usr/include/php/Zend -I/usr/include/php/TSRM -DHAVE_CONFIG_H -DHAVE_CONFIG_H -DHAVE_CONFIG_H -c /usr/local/src/dbg/dbg.c -fPIC -DPIC -o .libs/dbg.o
/usr/local/src/dbg/dbg.c:17:17: php.h: No such file or directory
.....

/usr/local/src/dbg/dbg.c:17:17: php.h: No such file or directory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
php.h is a part of php sources, not dbg.

You need php-devel package to be installed first.
or just get original php sources and compile with them.