Sets one or more HTTP header fields forming part of the server response sent when the page is delivered to the client by the server. As with setcookie() , the header() function must be called before any other output is sent to the browser, although other PHP code can be used prior to sending the header. This is a useful function when you want the client to interpret the data sent from the server in a way that's different from the default action. For example, most servers by default send a "Content-type" header of "text/html". Using the header() function, you can tell the client to perform an action such as a redirect, or to expect a different document format. In addition, various headers controlling caching can also be sent. Not all headers are understood by all browsers, however, so results may be unpredictable.
If the overwrite parameter is set, previously set headers will be replaced. This can be useful for conditionally writing headers.
The overwrite parameter was added in version 4.0.4
PHP Functions Essential Reference. Copyright © 2002 by New Riders Publishing (Authors: Zak Greant, Graeme Merrall, Torben Wilson, Brett Michlitsch). This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/). The authors of this book have elected not to choose any options under the OPL. This online book was obtained from http://www.fooassociates.com/phpfer/ and is designed to provide information about the PHP programming language, focusing on PHP version 4.0.4 for the most part. The information is provided on an as-is basis, and no warranty or fitness is implied. All persons and entities shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained in this book.