'collapseSpaces' => true,
			'replacements' => array(
				' ' => ' '
			),
			'finishReplacements' => array(), // replacements applied at very end (internal)
		);

		// merge options using arrays
		foreach(array('replacements') as $key) {
			if(!isset($options[$key])) continue;
			$options[$key] = array_merge($defaults[$key], $options[$key]);
		}
		
		$options = array_merge($defaults, $options);

		if(strpos($str, '>') !== false) {

			// strip out everything up to and including , if present
			if(strpos($str, '') !== false) list(, $str) = explode('', $str);

			// ensure tags are separated by whitespace
			$str = str_replace('><', '> <', $str);

			// normalize newlines
			if(strpos($str, "\r") !== false) {
				$str = str_replace(array("\r\n", "\r"), "\n", $str);
			}

			// normalize tabs to spaces
			if(strpos($str, "\t") !== false) {
				$str = str_replace("\t", " ", $str);
			}

			// ensure paragraphs and headers are followed by two newlines
			if(stripos($str, ')!i', '$1' . $options['splitBlocks'], $str);
			}

			// ensure list items are on their own line and prefixed with a bullet
			if(stripos($str, ']*>[\s\r\n]*!i', "\n
$prefix", $str);
				if($prefix) $options['replacements']["\n$prefix "] = "\n$prefix"; // prevent extra space
			}

			// convert 
 tags to be just a single newline
			if(stripos($str, '', '
', '
', '
'), "
\n", $str);
				while(stripos($str, "\n
") !== false) $str = str_replace("\n
", "
", $str);
				while(stripos($str, "
\n\n") !== false) $str = str_replace("
\n\n", "
\n", $str);
			}

			// make headlines more prominent with underlines or uppercase
			if(($options['uppercaseHeadlines'] || $options['underlineHeadlines']) && stripos($str, ']*>(.+?)!is', $str, $matches)) {
					foreach($matches[2] as $key => $headline) {
						$fullMatch = $matches[0][$key];
						$tagName = strtolower($matches[1][$key]);
						$underline = '';
						if($options['underlineHeadlines']) {
							$char = $tagName === $topHtag ? '=' : '-';
							$underline = "\n" . str_repeat($char, $this->strlen($headline));
						}
						if($options['uppercaseHeadlines']) $headline = strtoupper($headline);
						$str = str_replace($fullMatch, "<$tagName>$headline$underline", $str);
					}
				}
			}
		
			// convert "text" tags to "text (url)"
			if($options['linksToUrls'] && stripos($str, ']*href=([^\s>]+)[^<>]*>(.+?)!is', $str, $matches)) {
					$links = array();
					foreach($matches[0] as $key => $fullMatch) {
						$href = trim($matches[1][$key], '"\'');
						if(strpos($href, '#') === 0) continue; // do not convert jumplinks
						$anchorText = $matches[2][$key];
						$links[$fullMatch] = "$anchorText ($href)";
					}
					if(count($links)) {
						$str = str_replace(array_keys($links), array_values($links), $str); 
					}
				}
			}
		
			// indent within 
...
 sections
			if(strlen($options['preIndent']) && strpos($str, '|\s[^>]*>)(.+?)