php 字符串匹配相似度

<?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);
        }
    }
}
/**
 * 字符串排序
 * @description 将答案 ADCB 转换成 ABCD
 * @param string $string
 * @param string $sort asc|desc
 * @return string
 */
function answerSort($string = '',$sort = 'asc'){
    if(empty($string)){
        return '';
    }
    //拆分成数组，然后排序
    $arr = mb_str_split($string);
    if($sort == 'asc'){
        sort($arr);//值升序
    }else{
        rsort($arr);//值降序
    }
    //返回新字符串
    $string = implode('',$arr);
    return $string;
}

/**
 * 将字符串分割为数组
 * @param  string $str 字符串[支持中文字符串]
 * @return array 分割得到的数组
 */
function mb_str_split($str)
{
    return preg_split('/(?<!^)(?!$)/u', $str);
}
$c = answerSort("几天奶奶3天气sa1");
$b = answerSort("气几天13sa");
$lcs = new LCS();
//返回最长公共子序列
echo $lcs->getLCS($c, $b);