PHP 求字符串的相似度 函数

<?php
class LCS {
  var $str1;
  var $str2;
  var $c = array();
  /*返回串一和串二的最长公共子序列
*/
  function getLCS($str1, $str2, $len1 = 0, $len2 = 0) {
    $this->str1 = $str1;
    $this->str2 = $str2;
    if ($len1 == 0) $len1 = strlen($str1);
    if ($len2 == 0) $len2 = strlen($str2);
    $this->initC($len1, $len2);
    return $this->printLCS($this->c, $len1 - 1, $len2 - 1);
  }
  /*返回两个串的相似度
*/
  function getSimilar($str1, $str2) {
    $len1 = strlen($str1);
    $len2 = strlen($str2);
    $len = strlen($this->getLCS($str1, $str2, $len1, $len2));
    return $len * 2 / ($len1 + $len2);
  }
  function initC($len1, $len2) {
    for ($i = 0; $i < $len1; $i++) $this->c[$i][0] = 0;
    for ($j = 0; $j < $len2; $j++) $this->c[0][$j] = 0;
    for ($i = 1; $i < $len1; $i++) {
      for ($j = 1; $j < $len2; $j++) {
        if ($this->str1[$i] == $this->str2[$j]) {
          $this->c[$i][$j] = $this->c[$i - 1][$j - 1] + 1;
        } else if ($this->c[$i - 1][$j] >= $this->c[$i][$j - 1]) {
          $this->c[$i][$j] = $this->c[$i - 1][$j];
        } else {
          $this->c[$i][$j] = $this->c[$i][$j - 1];
        }
      }
    }
  }
  function printLCS($c, $i, $j) {
    if ($i == 0 || $j == 0) {
      if ($this->str1[$i] == $this->str2[$j]) return $this->str2[$j];
      else return "";
    }
    if ($this->str1[$i] == $this->str2[$j]) {
      return $this->printLCS($this->c, $i - 1, $j - 1).$this->str2[$j];
    } else if ($this->c[$i - 1][$j] >= $this->c[$i][$j - 1]) {
      return $this->printLCS($this->c, $i - 1, $j);
    } else {
      return $this->printLCS($this->c, $i, $j - 1);
    }
  }
} 
 
$lcs = new LCS();
//返回最长公共子序列
$lcs->getLCS("hello word","hello china");
//返回相似度
echo $lcs->getSimilar("吉林禽业公司火灾已致112人遇难","吉林宝源丰禽业公司火灾已致112人遇难");
echo 
$first = "abcdefg"; 
 $second = "aeg"; 
 echo similar_text($first, $second);
 //结果输出3.如果想以百分比显示，则可使用它的第三个参数,如下： 
$first = "abcdefg"; 
 $second = "aeg"; 
 similar_text($first, $second, $percent); 
 echo $percent; 
 
 echo levenshtein("Hello World","ello World"); 
 echo "<br />"; 
 echo levenshtein("Hello World","ello World",10,20,30); 
?>