Once you have completed the necessary installation of your server software it is worth running a quick test to ensure that all the necessary, minimum requirements are met.
You can do this very simply by creating a basic PHP script:
// Show all information
Save this, as phpinfo.php for example, in the file to the root of your Web site, then simply enter the address of your Web site into your browser as follows: http://www.yourdomain.com/phpinfo.php or http://localhost/phpinfo.php and you should receive a detailed summary and state of all the PHP compilation options and extensions (such as the Zlib, XML, and MySQL modules), the PHP version in use, server information and environment (if t is compiled as a module), the PHP environment, Operating System version information, paths, master and local values of configuration options, HTTP headers, and the PHP License. See the next page for a (very) compressed view of the information that this script outputs. The actual output is a single column and extends over a number of pages!
For a full description of all the elements that are output, visit the explanatory page at http://uk3.php.net/phpinfo.
Note: Remove the phpinfo.php file from your web root as soon as you have the necessary information. Leaving it in situ is a security risk. Your Joomla! installation has a built in version of the same script in the Help Menus for future reference.