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Configuring Apache
To tell Apache what to do on a 404 error, use the ErrorDocument directive:

ErrorDocument 404 /error-404.php

This tells Apache to serve up error-404.php in the document root directory when it encounters a 404 error. The ErrorDocument directive can go in Apache's httpd.conf file, but it also works in .htaccess files in individual directories. You can have a site-wide error-handling page or different error-handling pages for different parts of your site. Apache also sets some server variables that the error-handling page can access:

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REDIRECT_URL: the URL-path that was not found. If a user asks for the nonexistent page http://www.example.com/lunch/pastrami.html, for example, this variable is set to /lunch/pastrami.html.
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REDIRECT_STATUS: the HTTP response status resulting from the request for the original page. In our case, this is always "404". You can use ErrorDocument with other status codes, though, so if you have one error-handling page for multiple statuses, you can use this variable to determine which error status caused the error-handling page to be loaded.
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REDIRECT_ERROR_NOTES: a brief description of what went wrong, for example, "File does not exist: /usr/local/apache/docroot/lunch/pastrami.html".
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REDIRECT_REQUEST_METHOD: the method of the request for the original page, such as GET or POST.

If there is a query string in the original request, it is stored in REDIRECT_QUERY_STRING. The error page does not have access to the GET or POST variables via $_GET, $_POST, or $_REQUEST, but cookie variables are still available in $_COOKIE.

These REDIRECT variables are available in the PHP superglobal array $_SERVER: $_SERVER['REDIRECT_URL'], $_SERVER['REDIRECT_STATUS'], and so forth.