grab apache_1.3.19 from httpd.apache.org.
Afterwards, untar the php tarball and configure php with apache.
(./configure --with-apache=/usr/local/apache)
(btw, the tar sources for apache and php should both be untared in /usr/local)
then, after you've ./configure'd it, do make and make install. If that works out, then go to the apache directory, and do
./configure --activate-module=src/modules/php4/libphp4.a
Then run make and make install.
If all that works out, then go into your /usr/local/apache/conf/httpd.conf and uncomment the line that says:
AddType application/x-httpd-php .php
to
AddType application/x-httpd-php .php
Afterwards, start apache again and you're all set! If you have any questions, feel free to e-mail me.