I tried to instal PHP with the sequence above:
############
mkdir  /usr/apache/www/static/; cd  /usr/apache/www/static/
tar xvf /src/php-4.0.1pl2.tar 
tar xvf /src/apache_1.3.12.tar
cd /usr/apache/www/static/apache_1.3.12
./configure --prefix=/usr/apache  \
                   --enable-module=most \
                   --enable-suexec \
                   --suexec-caller=www \
                   --suexec-userdir=/usr/apache \
                   --suexec-docroot=/usr/apache/share/htdocs \
                   --suexec-logfile=/usr/apache/var/log/suexec_log \
              --suexec-safepath="/bin:/usr/bin:/usr/local/bin:/usr/apache/bin"
cd  /usr/apache/www/static/php-4.0.1pl2/
./configure  --prefix=/usr/apache   --with-pgsql  \
         --enable-track-vars \
        --with-apache=../apache_1.3.12
make
make install 
cd /usr/apache/www/static/apache_1.3.12
./configure --prefix=/usr/apache  \
                   --enable-module=most \
                   --enable-suexec \
                   --suexec-caller=www \
                   --suexec-userdir=/usr/apache \
                   --suexec-docroot=/usr/apache/share/htdocs \
                   --suexec-logfile=/usr/apache/var/log/suexec_log \
             --suexec-safepath="/bin:/usr/bin:/usr/local/bin:/usr/apache/bin"\
                  --activate-module=src/modules/php4/libmodphp4.a
make
#################
When it finish, there is the message above:
ar cr libproxy.a mod_proxy.o proxy_cache.o proxy_connect.o proxy_ftp.o proxy_http.o proxy_util.o
ranlib libproxy.a
<=== src/modules/proxy
===> src/modules/php4
gcc -c  -I../../os/unix -I../../include   -DSOLARIS2=270 -DUSE_EXPAT -I../../lib/expat-lite -DNO_DL_NEEDED `../../apaci`  mod_php4.c
cp libmodphp4.a libphp4.a
ar r libphp4.a mod_php4.o
ranlib libphp4.a
<=== src/modules/php4
<=== src/modules
gcc -c  -I./os/unix -I./include   -DSOLARIS2=270 -DUSE_EXPAT -I./lib/expat-lite -DNO_DL_NEEDED `./apaci` modules.c
gcc -c  -I./os/unix -I./include   -DSOLARIS2=270 -DUSE_EXPAT -I./lib/expat-lite -DNO_DL_NEEDED `./apaci` buildmark.c
gcc  -DSOLARIS2=270 -DUSE_EXPAT -I./lib/expat-lite -DNO_DL_NEEDED `./apaci`    \
      -o httpd buildmark.o modules.o modules/proxy/libproxy.a modules/php4/libphp4.a modules/standard/libstandard.a main/libmain.a ./os/unix/libos.a ap/libap.a  lib/expat-lite/libexpat.a  -lsocket -lnsl
Undefined                       first referenced
 symbol                             in file
modphp4_module                      modules.o
ld: fatal: Symbol referencing errors. No output written to httpd
make[2]: *** [target_static] Error 1
make[2]: Leaving directory `/home/aries/www/static/apache_1.3.12/src'
make[1]: *** [build-std] Error 2
make[1]: Leaving directory `/home/aries/www/static/apache_1.3.12'
make: *** [build] Error 2
#################
I didn't find php.ini file. The modules I used was
--with-pgsql    --with-apache=../apache_1.3.12/ --enable-track-vars