installed tar balls
   apache_1.3.12
   mysql-3.22.32
   php-4.0.1

I followed the steps in FAQ section 6.7 and got stuck.

./configure --prefix=/usr/local/apache \
            --enabled-shared=max \
            --activate-module=src/modules/php4/libphp4.a

Last line of compile is:
gcc -DLINUX=2 -I/usr/local/src/php-4.0.1 -I/usr/local/src/php-4.0.1/main -I/usr/local/src/php-4.0.1/main -I/usr/local/php-4.0.1/Zend -I/usr/local/src/php-4.0.1/Zend -I/usr/local/php-4.0.1 -DUSE_EXPAT -I./lib/expat-lite './apaci' -rdynamic \
-o httpd buildmark.o modules.o modules/standard/libstandard.a modules/php4/libphp4.a main/libmain.a ./os/unix/libos.a ap/libap.a lib/expat-lite/libexpat-lite.a -Wl,-rpath,/usr/local/mysql/lib/mysql -rdynamic -L/usr/local/mysql/lib/mysql -Lmodules/php4 -L../modules/php4 -L../../modules/php4 -lmodphp4 -lgdbm -lpam -ldl -lmysqlclient -lgd -lresolv -lm -ldl -lcrypt -lnsl -lresolv -lm -lcrypt -ldl

Complete error message from gcc is:
modules/php4/libphp4.a(mod_php4.o)(.data+0x28): undefined referance to 'zend_error'

I hope this information is useful.