PHP4 confiuration line:
./configure --with-mysql --with-imap --with-apache=../apache_1.3.12 --enable-track-vars

Apache Configuration line:
./configure --prefix=/www --activate-module=src/modules/php4/libphp4.a

Error displayed by apache configuration:

Configuring for Apache, Version 1.3.12
 + using installation path layout: Apache (config.layout)
 + activated php4 module (modules/php4/libphp4.a)
Creating Makefile
Creating Configuration.apaci in src
Creating Makefile in src
 + configured for FreeBSD 4.0 platform
 + setting C compiler to gcc
 + setting C pre-processor to gcc -E
 + checking for system header files
 + adding selected modules
    o php4_module uses ConfigStart/End
 + checking sizeof various data types
 + doing sanity check on compiler and options
** A test compilation with your Makefile configuration
** failed.  The below error output from the compilation
** test will give you an idea what is failing. Note that
** Apache requires an ANSI C Compiler, such as gcc. 

cd ..; gcc  -funsigned-char -I/usr/local/ports/php-4.0.1pl2 -I/usr/local/ports/php-4.0.1pl2/main -I/usr/local/ports/php-4.0.1pl2/main -I/usr/local/ports/php-4.0.1pl2/Zend -I/usr/local/ports/php-4.0.1pl2/Zend -I/usr/local/ports/php-4.0.1pl2 -DUSE_EXPAT -I./lib/expat-lite -DNO_DL_NEEDED `./apaci`     -o helpers/dummy helpers/dummy.c   -R/usr/local/lib  -rdynamic -L/usr/local/lib -Lmodules/php4 -L../modules/php4 -L../../modules/php4 -lmodphp4  -lpam -lc-client4  -lm -lcrypt   -lcrypt
/usr/local/lib/libc-client4.so: undefined reference to `mm_expunged'
/usr/local/lib/libc-client4.so: undefined reference to `mm_diskerror'
/usr/local/lib/libc-client4.so: undefined reference to `mm_lsub'
/usr/local/lib/libc-client4.so: undefined reference to `mm_flags'
/usr/local/lib/libc-client4.so: undefined reference to `mm_fatal'
/usr/local/lib/libc-client4.so: undefined reference to `mm_nocritical'
/usr/local/lib/libc-client4.so: undefined reference to `mm_notify'
/usr/local/lib/libc-client4.so: undefined reference to `mm_searched'
/usr/local/lib/libc-client4.so: undefined reference to `mm_status'
/usr/local/lib/libc-client4.so: undefined reference to `mm_login'
/usr/local/lib/libc-client4.so: undefined reference to `mm_list'
/usr/local/lib/libc-client4.so: undefined reference to `mm_critical'
/usr/local/lib/libc-client4.so: undefined reference to `mm_exists'
/usr/local/lib/libc-client4.so: undefined reference to `mm_log'
/usr/local/lib/libc-client4.so: undefined reference to `mm_dlog'
*** Error code 1

Stop in /usr/local/ports/apache_1.3.12/src/helpers.
======== Error Output for sanity check ========
============= End of Error Report =============

 Aborting!