int header(string string);The Header() function is used at the top of an HTML file to send raw HTTP header strings. See the HTTP 1.1 Specification for more information on raw http headers. Note: Remember that the Header() function must be called before any actual output is sent either by normal HTML tags or from PHP. It is a very common error to read code with include() or with auto_prepend and have spaces or empty lines in this code that force output before header() is called.
header("Location: http://www.php.net"); /* Redirect browser to PHP web site */
exit; /* Make sure that code below does not get executed when we redirect. */PHP scripts often generate dynamic HTML that must not be cached by the client browser or any proxy caches between the server and the client browser. Many proxies and clients can be forced to disable caching with
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); // Date in the past
header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); // always modified
header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1
header("Pragma: no-cache"); // HTTP/1.0