一个验证身份证号的函数（通过城市判断）

/**
 * @desc 验证身份证号
* @author 网上搜集
* @time    2015-11-12 11:12
 * @return bool
 */
function checkIdCard($idcard){
    $idcard = $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 $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;
}