This works well: ./configure --with-apxs=/usr/sbin/apxs --with-system-regex --with-gd --enable-track-vars --with-config-file-path=/etc/httpd/conf --with-exec-dir=/home/httpd/php/bin --with-imap --enable-magick-quotes --with-ldap --with-mcrypt --with-mhash --with-mysql --with-snmp --with-zlib --enable-ucd-snmp-hack
But the same from within rpm (3.0.2 release 6.0) fails when it checks for the C preprocessor.

Specfile:
Summary:   PHP - with the long awaited Zend engine :)
Name:      mod_php4
Version:   4.0b1
Release:   1
URL:       http://www.php.net/
Source:    http://www.php.net/version4/downloads/php-%{version}.tar.gz
Copyright: ???
Group:     Networking/Daemons
Requires:  apache-mod_ssl >= 1.3.6.2.3.6, imap >= 4.5, MySQL >= 3.21.25, gd >= 1.6.1 etc.
Obsoletes: php, mod_php, mod_php3
BuildRoot: /var/tmp/%{name}-%{version}-root
%description
%prep
%setup -q -n php-%{version}
%build
./configure --with-all-options-as-mentioned-above
make

Output:
++ echo -n checking how to run the C preprocessor...
checking how to run the C preprocessor... ++ echo configure:2480: checking how t
o run the C preprocessor
++ test -n
++ test -z
+++ echo ${ac_cv_prog_CPP+set}
++ eval test "${ac_cv_prog_CPP+set}" = set
+++ test  = set
++ CPP=gcc -E
++ cat
++ ac_try=$CPP $CPPFLAGS conftest.c >/dev/null 2>conftest.out
++ eval echo configure:2501: "$CPP $CPPFLAGS conftest.c >/dev/null 2>conftest.ou
t"
+++ echo configure:2501: gcc -E  conftest.c >/dev/null 2>conftest.out
+++ grep -v ^ *+ conftest.out
+++ grep -v ^conftest.c$
++ ac_err=
Bad exit status from /var/tmp/rpm-tmp.73649 (%build)

My apologies if I have overlooked something.