I'd like to know how to do this as well. I didn't use --with-apache but I have no php executable to be found either. My configure was
./configure \
--with-pear \
--enable-calendar \
--with-gettext \
--with-mnogosearch \
--with-apxs=/usr/local/apache-1.3.20/bin/apxs \
--with-config-file-path=/etc \
--with-gd=/usr/local \
--with-jpeg-dir=/usr/local \
--with-png-dir=/usr/local \
--with-mysql=/usr/local/mysql \
--with-ldap \
--with-openssl \
--with-zlib \
--with-xml \
--with-snmp \
--enable-ucd-snmp-hack \
--enable-track-vars \
--enable-versioning \
--enable-ftp