以下是代码片段：

<?php
@author shjuto@gmail.com
@blog http://www.paitoubing.cn
@date 2010-------2012 地球
class similarity
{
    function ld($str1,$str2)
    {
        $str1len = strlen($str1);
        $str2len = strlen($str2);
 
        if($str1len == 0)
        {
            return $str2len;
        }
 
        if($str2len == 0)
        {
            return $str1len;
        }
 
 
        $distance = array();
 
        for($i = 0; $i <= $str1len;$i++)
        {
            $distance[$i][0] = $i;
        }
 
        for($j = 0; $j <= $str2len;$j++)
        {
            $distance[0][$j] = $j;
        }
 
        for($i = 1; $i <= $str1len;$i++)
        {
            $char1 = $str1[$i-1];
 
            for($j = 1;$j <= $str2len;$j++)
            {
                $char2 = $str2[$j-1];
                if($char1 == $char2)
             {
                 $temp = 0;
             }
             else
             {
                 $temp = 1;
             }
 
             $distance[$i][$j] = min($distance[$i-1][$j]+1,$distance[$i][$j-1]+1,$distance[$i-1][$j-1]+$temp);
            }
 
        }
        //print_r($distance);
        // 可以注释掉，下面table的内容，为了测试思路，直观显示数组内容，添加上去的
        echo '<table border=1>';
        foreach ($distance as $key=>$value)
        {
         echo '<tr>';
         foreach ($value as $h)
         {
          echo '<td>'.$h.'</td>';
         }
         echo '</tr>';
        }
        echo '';
 
        return $distance[$str1len][$str2len];
    }
 
    function sim($str1,$str2)
    {
        $ld = $this->ld($str1,$str2);
 
        return 1 - ($ld / max(strlen($str1),strlen($str2)));
    }
 
}
 
$similarity = new similarity();
$str1 = 'kitten';
$str2 = 'sitting';
print_r($similarity->ld($str1,$str2));
echo $similarity->sim($str1,$str2);