indexphp

Index.php is a common filename used for the default entry point of PHP-based web applications. In a typical setup, when a user requests a directory, the web server serves a file named index.php if it is configured to do so. The file usually contains PHP code that generates the initial response or acts as a front controller that routes the request to the appropriate part of the application.

On Apache servers, the DirectoryIndex directive controls which files are considered default for a directory, often including index.php. On Nginx, the configuration may direct requests to index.php for processing by the PHP interpreter through FastCGI. In many modern PHP applications, index.php serves as a front controller, meaning all requests pass through a single script which then dispatches to controllers or handlers. Frameworks such as Laravel and WordPress commonly place index.php in the public web root to centralize routing and bootstrapping.

Security considerations include preventing directory listings, restricting file permissions, and ensuring that only intended PHP code is executable. Keeping index.php in a designated public directory and properly configuring the server helps reduce the risk of exposing source code or configuration details. Regular updates and secure coding practices are important, as index.php often handles critical application logic.

Performance aspects involve PHP opcode caches like OPcache, which speed up repeated execution of index.php, and serving static assets directly from the web server to minimize PHP processing. In some setups, index.php is complemented by additional routing and caching layers to improve scalability.

See also: DirectoryIndex, Front controller pattern, PHP.