headerphp

Header.php is a filename commonly used in PHP-based web applications to centralize HTTP header management and request initialization. The file is usually included at the beginning of a request so that the server can send appropriate HTTP headers before any body content is produced. Typical responsibilities of header.php include setting the content type and character encoding, controlling caching, issuing redirects, and performing early setup tasks such as starting sessions, configuring error reporting, loading configuration, or bootstrapping autoloaders.

In practice, header.php is often a simple script that calls PHP's header() function to emit one or more HTTP headers. For example, it may set the Content-Type to text/html; charset=UTF-8, enforce security-related headers like X-Content-Type-Options, or issue a Location header for redirects. It is important that header() calls occur before any echo, HTML, or whitespace is sent to the client. If a redirect is used, it should be followed by exit to halt further processing.

In the WordPress ecosystem, header.php also has a distinct meaning: within themes, header.php is a template file that outputs the HTML head section and the opening of the page body, and is loaded by the theme system via get_header(). This use pattern serves as a reusable part of the overall page layout rather than a pure HTTP header manager.

See also: header function, HTTP headers, output buffering, setcookie.