Trying to compile 4.3.2 with Apache HTTPD 2.0.45 (compiled from source with RedHat config.layout) as DSO with apxs on RedHat 7.3, completely updated through up2date including newest 2.4.20 kernel. Other installed software includes: Sybase ASE 12.5 Developer Edition and Sybase Open Client, Samba 2.2.8a rpm. All installed software is configured and running. Base system is a default RedHat 7.3 server install with no extra features. To be able to run PHP 4.3.2 the way I want, I installed several rpm's from RedHat 8.0:
- ncurses
- curl
- imap
- freetype2
- libmcrypt (from www.horde.org)
- mcal (from www.horde.org)

Hardware is a Compaq Proliant 2500R PentiumPro 200/384MB/Smart 2P controller/3x4 RAID0 and 2x9 RAID0/TLAN 100Mbit NIC. Server has to be booted with following kernel parameters: mem=exactmap mem=640k@0 mem=383M@1M

Compile features (default RH7.3 with some extra's):
./configure i386-redhat-linux   \
--prefix=/usr \
--exec-prefix=/usr \
--bindir=/usr/bin \
--sbindir=/usr/sbin  \
--sysconfdir=/etc \
--datadir=/usr/share \
--includedir=/usr/include \
--libdir=/usr/lib  \
--libexecdir=/usr/libexec \
--localstatedir=/var  \
--sharedstatedir=/usr/com \
--mandir=/usr/share/man  \
--infodir=/usr/share/info \
--prefix=/usr  \
--with-config-file-path=/etc \
--enable-force-cgi-redirect  \
--disable-debug  \
--enable-pic \
--disable-rpath  \
--enable-inline-optimization \
--with-bz2  \
--with-db3  \
--with-curl  \
--with-dom=/usr  \
--with-exec-dir=/usr/bin  \
--with-freetype-dir=/usr  \
--with-png-dir=/usr  \
--with-gd  \
--enable-gd-native-ttf  \
--with-ttf  \
--with-gdbm  \
--with-gettext  \
--with-ncurses  \
--with-gmp  \
--with-iconv  \
--with-jpeg-dir=/usr  \
--with-mm  \
--with-openssl  \
--with-png  \
--with-pspell  \
--with-regex=system   \
--with-xml   \
--with-expat-dir=/usr   \
--with-zlib  \
--with-layout=GNU   \
--enable-bcmath  \
--enable-debugger  \
--enable-exif   \
--enable-ftp  \
--disable-magic-quotes  \
--disable-safe-mode  \
--enable-sockets  \
--enable-sysvsem  \
--enable-sysvshm   \
--enable-discard-path  \
--enable-track-vars  \
--enable-trans-sid   \
--enable-yp  \
--enable-wddx  \
--without-oci8  \
--with-imap=/usr/lib  \
--with-imap-ssl  \
--with-kerberos=/usr/kerberos  \
--with-ldap   \
--with-mysql   \
--with-sybase-ct=/opt/sybase-12.5/OCS \
--enable-memory-limit  \
--enable-bcmath  \
--enable-shmop  \
--enable-versioning  \
--enable-calendar  \
--with-mcal=/usr  \
--with-mcrypt=/usr/lib  \
--enable-dbx  \
--enable-dio  \
--enable-mbstring  \
--enable-mbstr-enc-trans  \
--with-apxs2=/usr/sbin/apxs

Configure command executes perfectly with no warnings.
Make stops with the following output:

/bin/sh /tmp/php-4.3.2/libtool --silent --preserve-dup-deps --mode=compile gcc  -IZend/ -I/tmp/php-4.3.2/Zend/ -DPHP_ATOM_INC -I/tmp/php-4.3.2/include -I/tmp/php-4.3.2/main -I/tmp/php-4.3.2 -I/usr/include/apache -I/tmp/php-4.3.2/Zend -I/usr/include/libxml2 -I/usr/include/freetype2 -I/usr/include/imap -I/usr/kerberos/include -I/usr/include/mcal -I/usr/include/pspell -I/opt/sybase-12.5/OCS/include  -I/tmp/php-4.3.2/TSRM  -g -O2  -prefer-pic -c /tmp/php-4.3.2/Zend/zend_execute.c -o Zend/zend_execute.lo 
/bin/sh /tmp/php-4.3.2/libtool --silent --preserve-dup-deps --mode=compile gcc  -Isapi/apache2handler/ -I/tmp/php-4.3.2/sapi/apache2handler/ -DPHP_ATOM_INC -I/tmp/php-4.3.2/include -I/tmp/php-4.3.2/main -I/tmp/php-4.3.2 -I/usr/include/apache -I/tmp/php-4.3.2/Zend -I/usr/include/libxml2 -I/usr/include/freetype2 -I/usr/include/imap -I/usr/kerberos/include -I/usr/include/mcal -I/usr/include/pspell -I/opt/sybase-12.5/OCS/include  -I/tmp/php-4.3.2/TSRM  -g -O2  -prefer-pic -c /tmp/php-4.3.2/sapi/apache2handler/sapi_apache2.c -o sapi/apache2handler/sapi_apache2.lo 
In file included from /usr/include/apache/httpd.h:86,
                 from /usr/include/apache/util_filter.h:61,
                 from /tmp/php-4.3.2/sapi/apache2handler/sapi_apache2.c:40:
/usr/include/apache/pcreposix.h:41: conflicting types for `REG_BADBR'
/usr/include/regex.h:307: previous declaration of `REG_BADBR'
/usr/include/apache/pcreposix.h:42: conflicting types for `REG_BADPAT'
/usr/include/regex.h:299: previous declaration of `REG_BADPAT'
/usr/include/apache/pcreposix.h:43: conflicting types for `REG_BADRPT'
/usr/include/regex.h:310: previous declaration of `REG_BADRPT'
/usr/include/apache/pcreposix.h:44: conflicting types for `REG_EBRACE'
/usr/include/regex.h:306: previous declaration of `REG_EBRACE'
/usr/include/apache/pcreposix.h:45: conflicting types for `REG_EBRACK'
/usr/include/regex.h:304: previous declaration of `REG_EBRACK'
/usr/include/apache/pcreposix.h:46: conflicting types for `REG_ECOLLATE'
/usr/include/regex.h:300: previous declaration of `REG_ECOLLATE'
/usr/include/apache/pcreposix.h:47: conflicting types for `REG_ECTYPE'
/usr/include/regex.h:301: previous declaration of `REG_ECTYPE'
/usr/include/apache/pcreposix.h:48: conflicting types for `REG_EESCAPE'
/usr/include/regex.h:302: previous declaration of `REG_EESCAPE'
/usr/include/apache/pcreposix.h:50: conflicting types for `REG_EPAREN'
/usr/include/regex.h:305: previous declaration of `REG_EPAREN'
/usr/include/apache/pcreposix.h:51: conflicting types for `REG_ERANGE'
/usr/include/regex.h:308: previous declaration of `REG_ERANGE'
/usr/include/apache/pcreposix.h:52: conflicting types for `REG_ESIZE'
/usr/include/regex.h:314: previous declaration of `REG_ESIZE'
/usr/include/apache/pcreposix.h:53: conflicting types for `REG_ESPACE'
/usr/include/regex.h:309: previous declaration of `REG_ESPACE'
/usr/include/apache/pcreposix.h:54: conflicting types for `REG_ESUBREG'
/usr/include/regex.h:303: previous declaration of `REG_ESUBREG'
/usr/include/apache/pcreposix.h:57: conflicting types for `REG_NOMATCH'
/usr/include/regex.h:295: previous declaration of `REG_NOMATCH'
/usr/include/apache/pcreposix.h:66: conflicting types for `regex_t'
/usr/include/regex.h:396: previous declaration of `regex_t'
/usr/include/apache/pcreposix.h:70: warning: redefinition of `regoff_t'
/usr/include/regex.h:399: warning: `regoff_t' previously declared here
/usr/include/apache/pcreposix.h:75: conflicting types for `regmatch_t'
/usr/include/regex.h:427: previous declaration of `regmatch_t'
/usr/include/apache/pcreposix.h:79: conflicting types for `regcomp'
/usr/include/regex.h:542: previous declaration of `regcomp'
/usr/include/apache/pcreposix.h:80: conflicting types for `regexec'
/usr/include/regex.h:546: previous declaration of `regexec'
/usr/include/apache/pcreposix.h:81: conflicting types for `regerror'
/usr/include/regex.h:551: previous declaration of `regerror'
/usr/include/apache/pcreposix.h:82: conflicting types for `regfree'
/usr/include/regex.h:554: previous declaration of `regfree'
make: *** [sapi/apache2handler/sapi_apache2.lo] Error 1


I previously did a succesful compile of PHP 4.3.1 against Apache 2.0.44 on RH7.3 with exactly the same configure options.