<?php
// strip javascript, styles, html tags, normalize entities and spaces
// based on http://www.php.net/manual/en/function.strip-tags.php#68757
function html2text($html){
	$text = $html;
	static $search = array(
		'@<script.+?</script>@usi',  // Strip out javascript content
		'@<style.+?</style>@usi',    // Strip style content
		'@<!--.+?-->@us',            // Strip multi-line comments including CDATA
		'@</?[a-z].*?\>@usi',         // Strip out HTML tags
	);
	$text = preg_replace($search, ' ', $text);
	// normalize common entities
	$text = normalizeEntities($text);
	// decode other entities
	$text = html_entity_decode($text, ENT_QUOTES, 'utf-8');
	// normalize possibly repeated newlines, tabs, spaces to spaces
	$text = preg_replace('/\s+/u', ' ', $text);
	$text = trim($text);
	// we must still run htmlentities on anything that comes out!
	// for instance:
	// <<a>script>alert('XSS')//<<a>/script>
	// will become
	// <script>alert('XSS')//</script>
	return $text;
} 
 
// replace encoded and double encoded entities to equivalent unicode character
// also see /app/bookmarkletPopup.js
function normalizeEntities($text) {
	static $find = array();
	static $repl = array();
	if (!count($find)) {
		// build $find and $replace from map one time
		$map = array(
			array('\'', 'apos', 39, 'x27'), // Apostrophe
			array('\'', '‘', 'lsquo', 8216, 'x2018'), // Open single quote
			array('\'', '’', 'rsquo', 8217, 'x2019'), // Close single quote
			array('"', '“', 'ldquo', 8220, 'x201C'), // Open double quotes
			array('"', '”', 'rdquo', 8221, 'x201D'), // Close double quotes
			array('\'', '‚', 'sbquo', 8218, 'x201A'), // Single low-9 quote
			array('"', '„', 'bdquo', 8222, 'x201E'), // Double low-9 quote
			array('\'', '′', 'prime', 8242, 'x2032'), // Prime/minutes/feet
			array('"', '″', 'Prime', 8243, 'x2033'), // Double prime/seconds/inches
			array(' ', 'nbsp', 160, 'xA0'), // Non-breaking space
			array('-', '‐', 8208, 'x2010'), // Hyphen
			array('-', '–', 'ndash', 8211, 150, 'x2013'), // En dash
			array('--', '—', 'mdash', 8212, 151, 'x2014'), // Em dash
			array(' ', ' ', 'ensp', 8194, 'x2002'), // En space
			array(' ', ' ', 'emsp', 8195, 'x2003'), // Em space
			array(' ', ' ', 'thinsp', 8201, 'x2009'), // Thin space
			array('*', '•', 'bull', 8226, 'x2022'), // Bullet
			array('*', '‣', 8227, 'x2023'), // Triangular bullet
			array('...', '…', 'hellip', 8230, 'x2026'), // Horizontal ellipsis
			array('°', 'deg', 176, 'xB0'), // Degree
			array('€', 'euro', 8364, 'x20AC'), // Euro
			array('Â¥', 'yen', 165, 'xA5'), // Yen
			array('£', 'pound', 163, 'xA3'), // British Pound
			array('©', 'copy', 169, 'xA9'), // Copyright Sign
			array('®', 'reg', 174, 'xAE'), // Registered Sign
			array('â„¢', 'trade', 8482, 'x2122') // TM Sign
		);
		foreach ($map as $e) {
			for ($i = 1; $i < count($e); ++$i) {
				$code = $e[$i];
				if (is_int($code)) {
					// numeric entity
					$regex = "/&(amp;)?#0*$code;/";
				}
				elseif (preg_match('/^.$/u', $code)/* one unicode char*/) {
					// single character
					$regex = "/$code/u";
				}
				elseif (preg_match('/^x([0-9A-F]{2}){1,2}$/i', $code)) {
					// hex entity
					$regex = "/&(amp;)?#x0*" . substr($code, 1) . ";/i";
				}
				else {
					// named entity
					$regex = "/&(amp;)?$code;/";
				}
				$find[] = $regex;
				$repl[] = $e[0];
			}
		}
	} // end first time build
	return preg_replace($find, $repl, $text);	
}