PHP 中国公民身份证号 验证

<?php
/**
 * check string is a PRC ID num
 * 网上看到的，修正了一些bug，改写为类。
 *
 * @author windk
 * @version 1.0
 * date:2011-06-13
 */
class Idcheck {

    private $idNum;

    public function __construct($idNum) {
        $this->idNum = (string)$idNum;
    }

    public function isIdNum() {
        $idNum = $this->idNum;
        if (strlen($idNum) == 18) {
            return $this->idcardCheckSum18($idNum);
        } elseif ((strlen($idNum) == 15))    {
            $idNum = $this->idcard_15to18($idNum);
            return $this->idcardCheckSum18('"' . $idNum . '"');
        } else    {
            return false;
        }
    }

    // 计算身份证校验码，根据国家标准GB 11643-1999
    public function idcardVerifyNumber($idcardBase)
    {
        if(strlen($idcardBase) != 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; $i < strlen($idcardBase); $i++)
        {
            $checksum += substr($idcardBase, $i, 1) * $factor[$i];
        }
        $mod = $checksum % 11;
        $verify_number = $verify_number_list[$mod];
        return $verify_number;
    }

    // 将15位身份证升级到18位
    public function idcard_15to18($idcard){
        if (strlen($idcard) != 15){
            return false;
        }else{

            // 如果身份证顺序码是996 997 998 999，这些是为百岁以上老人的特殊编码
            if (array_search(substr($idcard, 12, 3), array('996', '997', '998', '999')) !== false){
            $idcard = substr($idcard, 0, 6) . '18'. substr($idcard, 6, 9);
            }else{
            $idcard = substr($idcard, 0, 6) . '19'. substr($idcard, 6, 9);
            }
        }
        $idcard = $idcard . idcard_verify_number($idcard);
        return $idcard;
    }

    // 18位身份证校验码有效性检查
    public function idcardCheckSum18($idcard){
        if (strlen($idcard) != 18){ return false; }
        $idcard_base = substr($idcard, 0, 17);
        if ($this->idcardVerifyNumber($idcard_base) != strtoupper(substr($idcard, 17, 1))){
            return false;
        }else{
            return true;
        }
    }
}
?>