身份证号验证（兼容15位，18位）

身份证号验证，兼容15位，18位！
protected function checkIdCard(){
if(empty($_POST['idcard'])){
return false;
}
$idcard = $_POST['idcard'];
$City = array(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");
$iSum = 0;
$idCardLength = strlen($idcard);
//长度验证
if(!preg_match('/^\d{17}(\d|x)$/i',$idcard) and !preg_match('/^\d{15}$/i',$idcard))
{
return false;
}
//地区验证
if(!array_key_exists(intval(substr($idcard,0,2)),$City))
{
return false;
}
// 15位身份证验证生日，转换为18位
if ($idCardLength == 15)
{
$sBirthday = '19'.substr($idcard,6,2).'-'.substr($idcard,8,2).'-'.substr($idcard,10,2);
$d = new DateTime($sBirthday);
$dd = $d->format('Y-m-d');
if($sBirthday != $dd)
{
return false;
}
$idcard = substr($idcard,0,6)."19".substr($idcard,6,9);//15to18
$Bit18 = getVerifyBit($idcard);//算出第18位校验码
$idcard = $idcard.$Bit18;
}
// 判断是否大于2078年，小于1900年
$year = substr($idcard,6,4);
if ($year<1900 || $year>2078 )
{
return false;
}

//18位身份证处理
$sBirthday = substr($idcard,6,4).'-'.substr($idcard,10,2).'-'.substr($idcard,12,2);
$d = new DateTime($sBirthday);
$dd = $d->format('Y-m-d');
if($sBirthday != $dd)
{
return false;
}
//身份证编码规范验证
$idcard_base = substr($idcard,0,17);
if(strtoupper(substr($idcard,17,1)) != getVerifyBit($idcard_base))
{
return false;
}
return $_POST['idcard'];
}

// 计算身份证校验码，根据国家标准GB 11643-1999
function getVerifyBit($idcard_base)
{
if(strlen($idcard_base) != 17)
{
return false;
}
//加权因子
$factor = array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
//校验码对应值
$verify_number_list = array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
$checksum = 0;
for ($i = 0; $i < strlen($idcard_base); $i++)
{
$checksum += substr($idcard_base, $i, 1) * $factor[$i];
}
$mod = $checksum % 11;
$verify_number = $verify_number_list[$mod];
return $verify_number;
}