Editing URL redirection (section)

==== Using server-side scripting for redirection ====
Web authors producing HTML content can't usually create redirects using HTTP headers as these are generated automatically by the web server program when serving an HTML file.  The same is usually true even for programmers writing CGI scripts, though some servers allow scripts to add custom headers (e.g. by enabling "non-parsed-headers").  Many web servers will generate a 3xx status code if a script outputs a "Location:" header line.  For example, in [[PHP]], one can use the "header" function:

<syntaxhighlight lang="php">
header('HTTP/1.1 301 Moved Permanently');
header('Location: https://www.example.com/');
exit();
</syntaxhighlight>

More headers may be required to prevent caching.<ref name="php-301-robust-solution" /> The programmer must ensure that the headers are output before the body.  This may not fit easily with the natural flow of control through the code.  To help with this, some frameworks for server-side content generation can buffer the body data.  In the [[Active Server Pages|ASP scripting]] language, this can also be accomplished using <code>response.buffer=true</code> and <code>response.redirect <nowiki>"https://www.example.com/"</nowiki></code> HTTP/1.1 allows for either a relative URI reference or an absolute URI reference.<ref name="venDA" /> If the URI reference is relative the client computes the required absolute URI reference according to the rules defined in [https://tools.ietf.org/html/rfc3986 RFC 3986].<ref name="3Y1IG" />