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
     */

    public function getSimilar($str1, $str2) {
        $len1 = strlen($str1);
        $len2 = strlen($str2);
        $len = strlen($this->getLCS($str1, $str2, $len1, $len2));
        return round($len * 2 / ($len1 + $len2),2);
    }

    private 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];
                }
            }
        }
    }

    private 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);
        }
    }

}

$c = new LCS();
$t = $c->getSimilar('春秋航空：拟5000万元-1亿元回购股份', '春秋航空：拟5000万元-1亿元回购公司股份');
var_dump($t);
//float(0.94)