Hi,
Download and unpack the php source:
http://www.php.net/get/php-4.3.1.tar.gz/from/us2.php.net/mirror
Then go into the unpacked folder,
Then configure php with the modules you want, the config line from one of my servers is:
./configure --with-apxs=/usr/local/apache/bin/apxs --with-xml --enable-bcmath --enable-calendar --with-curl --with-swf=/usr/local/flash --enable-ftp --with-gd=../gd-2.0.4 --with-jpeg-dir=/usr/local --with-png-dir=/usr --with-xpm-dir=/usr/X11R6 --with-imap --with-imap-ssl --with-kerberos --enable-mbstring --enable-mbstr-enc-trans --enable-mbregex --with-mcrypt --with-ming=../ming-0.2a --enable-magic-quotes --with-mysql --with-pear --enable-xslt --with-xslt-sablot --enable-sockets --enable-track-vars --with-ttf --with-freetype-dir=/usr --enable-gd-native-ttf --enable-versioning --with-zlib
so, say you wanted domxml you would add on --with-domxml
etc until you have all of the modules needed
then type make
then type make install
then restart apache
if it runs through those steps without error you should now have a fully working php with the new modules
