Quicksilver string ranking algorithm in PHP

quicksilver_score.php

<?

// Quicksilver Score
//
// A port of the Quicksilver string ranking algorithm
// (re-ported from Javascript to PHP by Kenzie Campbell)
// http://route19.com/logbook/view/quicksilver-score-in-php
// 
// score("hello world","axl") //=> 0.0
// score("hello world","ow") //=> 0.6
// score("hello world","hello world") //=> 1.0
//
// The Javascript code is available here
// http://orderedlist.com/articles/live-search-with-quicksilver-style/
// http://orderedlist.com/demos/quicksilverjs/javascripts/quicksilver.js
//
// The Quicksilver code is available here
// http://code.google.com/p/blacktree-alchemy/
// http://blacktree-alchemy.googlecode.com/svn/trunk/Crucible/Code/NSString+BLTRRanking.m
//
// The MIT License
// 
// Copyright (c) 2008 Lachie Cox
// 
// 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 score($string,$abbreviation,$offset=0)
{
	$string = strtolower($string);
	$abbreviation = strtolower($abbreviation);
	if(strlen($abbreviation) == 0) return 0.9;
	if(strlen($abbreviation) > strlen($string)) return 0.0;
	for ($i = strlen($abbreviation); $i > 0; $i--)
	{
		$sub_abbreviation = substr($abbreviation,0,$i);
		$index = strpos($string,$sub_abbreviation);
		if($index<0 or $index===false) continue;
		if($index + strlen($abbreviation) > strlen($string) + $offset) continue;
		$next_string = substr($string,$index+strlen($sub_abbreviation));
		$next_abbreviation = null;
		if($i >= strlen($abbreviation)) $next_abbreviation = '';
		else $next_abbreviation = substr($abbreviation,$i);
		$remaining_score = score($next_string,$next_abbreviation,$offset+$index);
		if ($remaining_score > 0)
		{
			$score = strlen($string)-strlen($next_string);
			if($index != 0)
			{
				$j = 0;
				$c = ord(substr($string,$index-1));
				if($c==32 || $c == 9)
				{
					for($j=($index-2); $j >= 0; $j--)
					{
						$c = ord(substr($string,$j,1));
						$score -= (($c == 32 || $c == 9) ? 1 : 0.15);
					}
				}
				else $score -= $index;
			}
			$score += $remaining_score * strlen($next_string);
			$score /= strlen($string);
			return $score;
		}
	}
	return 0.0;
}

?>