normalize_url.php

<?php
/**
 * Copyright (c) 2011 Niklas A. Femerstrand <niklas@flattr.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/

function normalizeURL($url)
{
	$newUrl = "";
	$url = parse_url($url);	
	$defaultSchemes = array("http" => 80, "https" => 443);

	if(isset($url['scheme']))
	{
		$url['scheme'] = strtolower($url['scheme']);
		// Strip scheme default ports
		if(isset($defaultSchemes[$url['scheme']]) && isset($url['port']) && $defaultSchemes[$url['scheme']] == $url['port'])
			unset($url['port']);
		$newUrl .= "{$url['scheme']}://";
	}

	if(isset($url['host']))
	{
		$url['host'] = strtolower($url['host']);
		// Seems like a valid domain, properly validation should be made in higher layers.
		if(preg_match("/[a-z]+\Z/", $url['host']))
		{
			if(preg_match("/^www\./", $url['host']) && gethostbyname($url['host']) == gethostbyname(str_replace("www.", "", $url['host'])))
				$newUrl .= str_replace("www.", "", $url['host']);
			else
				$newUrl .= $url['host'];
		}
		else
			$newUrl .= $url['host'];
	}

	if(isset($url['port']))
		$newUrl .= ":{$url['port']}";

	if(isset($url['path']))
	{
		// Case normalization
		$url['path'] = preg_replace('/(%([0-9abcdef][0-9abcdef]))/ex', "'%'.strtoupper('\\2')", $url['path']);
		//Strip duplicate slashes
		while(preg_match("/\/\//", $url['path']))
			$url['path'] = preg_replace("/\/\//", "/", $url['path']);

		/*
		 * Decode unreserved characters, http://www.apps.ietf.org/rfc/rfc3986.html#sec-2.3
		 * Heavily rewritten version of urlDecodeUnreservedChars() in Glen Scott's url-normalizer.
		 */

		$u = array();
		for ($o = 65; $o <= 90; $o++)
			$u[] = dechex($o);
		for ($o = 97; $o <= 122; $o++)
			$u[] = dechex($o);
		for ($o = 48; $o <= 57; $o++)
			$u[] = dechex($o);
		$chrs = array('-', '.', '_', '~');
		foreach($chrs as $chr)
			$u[] = dechex(ord($chr));
		$url['path'] = preg_replace_callback(array_map(create_function('$str', 'return "/%" . strtoupper($str) . "/x";'), $u),
	                                                   create_function('$matches', 'return chr(hexdec($matches[0]));'), $url['path']);
	    // Remove directory index
		$defaultIndexes = array("/default\.aspx/" => "default.aspx", "/default\.asp/"  => "default.asp",
	                            "/index\.html/"   => "index.html",   "/index\.htm/"    => "index.htm",
	                            "/default\.html/" => "default.html", "/default\.htm/"  => "default.htm",
	                            "/index\.php/"    => "index.php",    "/index\.jsp/"    => "index.jsp");
		foreach($defaultIndexes as $index => $strip)
		{
			if(preg_match($index, $url['path']))
				$url['path'] = str_replace($strip, "", $url['path']);
		}
	
	    /**
	     * Path segment normalization, http://www.apps.ietf.org/rfc/rfc3986.html#sec-5.2.4
	     * Heavily rewritten version of removeDotSegments() in Glen Scott's url-normalizer.
	     */
		
		$new_path = '';
		while(!empty($url['path']))
		{
			if(preg_match('!^(\.\./|\./)!x', $url['path']))
				$url['path'] = preg_replace('!^(\.\./|\./)!x', '', $url['path']);
			elseif(preg_match('!^(/\./)!x', $url['path'], $matches) || preg_match('!^(/\.)$!x', $url['path'], $matches))
				$url['path'] = preg_replace("!^" . $matches[1] . "!", '/', $url['path']);
			elseif(preg_match('!^(/\.\./|/\.\.)!x', $url['path'], $matches))
			{
				$url['path'] = preg_replace( '!^' . preg_quote( $matches[1], '!' ) . '!x', '/', $url['path'] );
				$new_path = preg_replace( '!/([^/]+)$!x', '', $new_path );
			}
			elseif(preg_match('!^(\.|\.\.)$!x', $url['path']))
				$url['path'] = preg_replace('!^(\.|\.\.)$!x', '', $url['path']);
			else
			{
				if(preg_match('!(/*[^/]*)!x', $url['path'], $matches))
				{
					$first_path_segment = $matches[1];
					$url['path'] = preg_replace( '/^' . preg_quote( $first_path_segment, '/' ) . '/', '', $url['path'], 1 );
					$new_path .= $first_path_segment;
				}
			}
		}
		$newUrl .= $new_path;
	}
	
	if(isset($url['fragment']))
		unset($url['fragment']);
	
	// Sort GET params alphabetically, not because the RFC requires it but because it's cool!
	if(isset($url['query']))
	{
		if(preg_match("/&/", $url['query']))
		{
			$s = explode("&", $url['query']);
			$url['query'] = "";
			sort($s);
			foreach($s as $z)
				$url['query'] .= "{$z}&";
			$url['query'] = preg_replace("/&\Z/", "", $url['query']);
		}
		$newUrl .= "?{$url['query']}";
	}

	return $newUrl;
}