I set up Apache 1.3.0 (and 1.3.1) as described in the
FAQ (howto run 2.0.1 and 3.0.x at the same time), but
get the following error when compiling:

gcc -c  -I./os/unix -I./include   -DLINUX=2 -DUSE_HSREGEX  buildmark.c
gcc  -DLINUX=2 -DUSE_HSREGEX     \
      -o httpd buildmark.o modules.o modules/standard/libstandard.a modules/extra/libextra.a main/libmain.a ./os/unix/libos.a ap/libap.a regex/libregex.a  -lm
modules/extra/libextra.a(mod_php.o): In function `send_parsed_php':
mod_php.o(.text+0x1c1): undefined reference to `apache_php_module_main'
make: *** [target_static] Error 1