<?php

function login__from_env()

{

	return $_SERVER["PHP_AUTH_USER"]

		.($_SERVER["PHP_AUTH_PW"] !== "" ? ":".$_SERVER["PHP_AUTH_PW"] : "");

}

function user2path($user) # multiple @ and nested . OK: a@b.c@url -> url?b.c.a

{

	$path = $user;

	# remove padding used to visually separate elements: x__@y__@url -> x@y@url

	# also remove leading __ that indicates internal field: __x@url -> x@url

	# this leaves embedded __ (eg. x__y) untouched

	$path = preg_replace('/\b__|__\b/', '', $path);

	# remove insertion comments: [c]x[d]@url -> x@url

	# use [] because in writing, [] denotes insertion

	# insertion indicates that the semantic meaning of the [] portion also

	#  applies, even though it's not included in the linked term name

	$path = preg_replace('/\[.*?\]/', '', $path);

	# remove deletion comments: (-c_-)x@url -> c_x@url

	# use () because in editing, () denotes something to remove

	# the -...- indicate strikethrough (deletion)

	# deletion indicates that the semantic meaning of the () portion does not

	#  apply, even though it's included in the linked term name

	$path = preg_replace('/\(-([^)]*?)-\)/', '$1', $path);

	# translate reverse @-paths into forward .-paths

	$path = implode(".", array_reverse(explode("@", $path)));

	# undo transposes: y~x_@url -> x_y@url , Y~x@url -> xY@url

	# these can be used to put the category in a column name first

	# can't use : for this because Firefox will not update the "password" for

	#  the website with the new value after the :

	$path = preg_replace('/([^.]*)~([^.]*)/', '$2$1', $path);

	# apply substitutions: x."_y@url -> x.x_y@url

	# these can be used when a table name is repeated in a column name

	$path = preg_replace('/(([^.]+)\.[^.]*)"/', '$1$2', $path);

	return $path;

}

if (!isset($_SERVER["PHP_AUTH_USER"])) # browser first omits Authorization

{

	header('WWW-Authenticate: Basic realm="'

.'please leave username/password blank or as filled in. '

.'**IMPORTANT**: to visit the homepage of this site, you should always '

.'append \".\": \"'.$_SERVER["HTTP_HOST"].'.\" "');

}

else

{

	$dest = preg_replace('!\b/!', "./", $_SERVER["SCRIPT_URI"])."?";

		# append trailing . to host to prevent infinite redirect loop

	if ($_SERVER["PHP_AUTH_USER"] !== "") # prepend to query string

		$dest .= "."/*force dotpath*/.user2path(login__from_env());

	$dest .= $_SERVER["QUERY_STRING"];

	header("Location: ".$dest);

}

?>