While many popular website applications (WordPress, Drupal, Joomla, etc.) are open source and therefore freely available, running these PHP-based apps on a Windows IIS web server requires a bit of retrofitting.
Although Microsoft has streamlined the process of installing and configuring the PHP scripting language on IIS 7.0, many web administrators consider the fix, which involves enabling FastCGI extensions, too risky for production environments. Others simply wish to set up an independent test environment for evaluating open source apps.
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Moreover, PHP extensions are not the only hurdle for Windows webmasters. A large number of PHP-based open source apps rely on backend databases (MySQL, Maria DB, PostgreSQL, etc.) that also need special handling to run on Windows.
Enter WampServer, an open source product that installs a PHP-apps-ready platform consisting of Apache web server, MySQL database, PHP, plus several helpful GUI-based utilities. WampServer can be installed on virtually any version of Windows, either desktop or server. With an active user community, industrial-grade training programs and a large installed base, WampServer is one of the world's most popular Apache-MySQL-PHP distributions.