PHP is a very popular Apache module. You can basically embed PHP code into HTML using special tags. For more information on PHP, visit their homepage at http://www.php.net.
There are many options used to build PHP. For example, what type of database the system has. The options are beyond the scope of this document. Please read the INSTALL file that comes with the PHP tarball.
There are many additional tools you will have to install to enable certain features in PHP. For example, if you have to program with graphic files, I do recommend you to install GD (graphics library) with PHP4.
Untar the PHP package:
# cd /opt/apache # tar zxvf php-4.2.x.tar.gz # cd php-4.2.x