两个字符串相似度

    public $str1;
    public $str2;
    public $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);
        }
    }