PHP 身份证验证

function check_card($card)
{
        $city = [11 => "北京", 12 => "天津", 13 => "河北", 14 => "山西", 15 => "内蒙古", 21 => "辽宁", 22 => "吉林", 23 => "黑龙江 ", 31 => "上海", 32 => "江苏", 33 => "浙江", 34 => "安徽", 35 => "福建", 36 => "江西", 37 => "山东", 41 => "河南", 42 => "湖北 ", 43 => "湖南", 44 => "广东", 45 => "广西", 46 => "海南", 50 => "重庆", 51 => "四川", 52 => "贵州", 53 => "云南", 54 => "西藏 ", 61 => "陕西", 62 => "甘肃", 63 => "青海", 64 => "宁夏", 65 => "新疆", 71 => "台湾", 81 => "香港", 82 => "澳门", 91 => "国外 "];
        $tip = "";
        $match = "/^\d{6}(18|19|20)?\d{2}(0[1-9]|1[012])(0[1-9]|[12]\d|3[01])\d{3}(\d|X)$/";
        $pass = true;
        if (!$card || !preg_match($match, $card)) {
            //身份证格式错误
            $pass = false;
        } else if (!$city[substr($card, 0, 2)]) {
            //地址错误
            $pass = false;
        } else {
            //18位身份证需要验证最后一位校验位
            if (strlen($card) == 18) {
                $card = str_split($card);
                //∑(ai×Wi)(mod 11)
                //加权因子
                $factor = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
                //校验位
                $parity = [1, 0, 'X', 9, 8, 7, 6, 5, 4, 3, 2];
                $sum = 0;
                $ai = 0;
                $wi = 0;
                for ($i = 0; $i < 17; $i++) {
                    $ai = $card[$i];
                    $wi = $factor[$i];
                    $sum += $ai * $wi;
                }
                $last = $parity[$sum % 11];
                if ($parity[$sum % 11] != $card[17]) {
                    //                        $tip = "校验位错误";
                    $pass = false;
                }
            } else {
                $pass = false;
            }
        }
        if (!$pass) return false;/* 身份证格式错误*/
        return true;/* 身份证格式正确*/
    }