How to modify HTTP headers with PHP header() function

Many examples that show how to use the header() function of PHP.

Hint:
If you want to check your headers, you can use web based tools like: web-sniffer.net, web-browser extensions (e.g. LiveHTTPHeaders, ieHTTPHeaders) or another third-party software tool.

 

Source: http://www.jonasjohn.de/snippets/php/headers.htm

Related links:
https://en.wikipedia.org/wiki/List_of_HTTP_status_codes
http://www.web-caching.com/mnot_tutorial/
http://reeg.junetz.de/DSP/node16.html