PHP身份证验证

/**
     *  验证身份证是否有效
     * @param type $sid
*/
private function check_IDCard($sid) {
        if (strlen($sid) != 15 && strlen($sid) != 18) {
//如果位数不符合15 或者18
            return FALSE;
        }
        if (strlen($sid) == 15) {
            $wi = array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2, 1);
            $sid = substr_replace($sid, 19, 6, 0);
            $count = array();
            $sid[17] = 0; //定义第18位
            for ($i = 0; $i < 17; ++$i) {
                $count[] = $sid[$i] * $wi[$i];
            }
            $sum = array_sum($count) % 11;
            $zuihou = array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
            $sid = substr_replace($sid, $zuihou[$sum], 17, 1);
        }

        $wi18 = array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
        $sum2 = array();
        for ($j = 0; $j < 17; $j++) {
            $sum2[] = $sid[$j] * $wi18[$j];
        }
        $sum2 = array_sum($sum2) % 11;
        $yz = array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
        if ($yz[$sum2] == $sid[17]) {
//如果最后一位和验证号一样，则返回真
            return TRUE;
        } else {
            return false;
        }
    }