1、简单的正则表达式：

（1）preg_match("/^(\d{18,18}|\d{15,15}|\d{17,17}x)$/",$id_card)
（2）preg_match("/^(\d{6})(18|19|20)?(\d{2})([01]\d)([0123]\d)(\d{3}) (\d|X)?$/",$id_card)
（3）preg_match("/(^\d{15}$/)|(\d{17}(?:\d|x|X)$/),$id_card)

2、复杂并且严格一些的验证：

//这个可以验证15位和18位的身份证，并且包含生日和校验位的验证。  
//如果有兴趣，还可以加上身份证所在地的验证，就是前6位有些数字合法有些数字不合法。

function isIdCardNo(num)
{  
          num = num.toUpperCase();
         //身份证号码为15位或者18位，15位时全为数字，18位前17位为数字，最后一位是校验位，可能为数字或字符X。  
          if (!(/(^\d{15}$)|(^\d{17}([0-9]|X)$)/.test(num)))  
          {
               alert('输入的身份证号长度不对，或者号码不符合规定！\n15位号码应全为数字，18位号码末位可以为数字或X。');
              return false;
         }
//校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。
//下面分别分析出生日期和校验位
var len, re;
len = num.length;
if (len == 15)
{
re = new RegExp(/^(\d{6})(\d{2})(\d{2})(\d{2})(\d{3})$/);
var arrSplit = num.match(re);

//检查生日日期是否正确
var dtmBirth = new Date('19' + arrSplit[2] + '/' + arrSplit[3] + '/' + arrSplit[4]);
var bGoodDay;
bGoodDay = (dtmBirth.getYear() == Number(arrSplit[2])) && ((dtmBirth.getMonth() + 1) == Number(arrSplit[3])) && (dtmBirth.getDate() == Number(arrSplit[4]));
if (!bGoodDay)
{
          alert('输入的身份证号里出生日期不对！');  
           return false;
}
else
{
//将15位身份证转成18位
//校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。
          var arrInt = new Array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
           var arrCh = new Array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
           var nTemp = 0, i;  
            num = num.substr(0, 6) + '19' + num.substr(6, num.length - 6);
           for(i = 0; i < 17; i ++)
          {
                nTemp += num.substr(i, 1) * arrInt[i];
           }
           num += arrCh[nTemp % 11];  
            return num;  
}  
}
if (len == 18)
{
re = new RegExp(/^(\d{6})(\d{4})(\d{2})(\d{2})(\d{3})([0-9]|X)$/);
var arrSplit = num.match(re);

//检查生日日期是否正确
var dtmBirth = new Date(arrSplit[2] + "/" + arrSplit[3] + "/" + arrSplit[4]);
var bGoodDay;
bGoodDay = (dtmBirth.getFullYear() == Number(arrSplit[2])) && ((dtmBirth.getMonth() + 1) == Number(arrSplit[3])) && (dtmBirth.getDate() == Number(arrSplit[4]));
if (!bGoodDay)
{
alert(dtmBirth.getYear());
alert(arrSplit[2]);
alert('输入的身份证号里出生日期不对！');
return false;
}
else
{
//检验18位身份证的校验码是否正确。
//校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。
var valnum;
var arrInt = new Array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
var arrCh = new Array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
var nTemp = 0, i;
for(i = 0; i < 17; i ++)
{
nTemp += num.substr(i, 1) * arrInt[i];
}
valnum = arrCh[nTemp % 11];
if (valnum != num.substr(17, 1))
{
alert('18位身份证的校验码不正确！应该为：' + valnum);
return false;
}
return num;
}
}
return false;
}
3、严格的验证：
<script>
var aCity={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Unbsp;疆",71:"台湾",81:"香港",82:"澳门",91:"国外 "}

function cidInfo(sId){
var iSum=0
var info=""
if(!/^d{17}(d|x)$/i.test(sId))return false;
sId=sId.replace(/x$/i,"a");
if(aCity[parseInt(sId.substr(0,2))]==null)return "Error:非法地区";
sBirthday=sId.substr(6,4)+"-"+Number(sId.substr(10,2))+"-"+Number(sId.substr(12,2));
var d=new Date(sBirthday.replace(/-/g,"/"))
if(sBirthday!=(d.getFullYear()+"-"+ (d.getMonth()+1) + "-" + d.getDate()))return "Error:非法生日";
for(var i = 17;i>=0;i --) iSum += (Math.pow(2,i) % 11) * parseInt(sId.charAt(17 - i),11)
if(iSum%11!=1)return "Error:非法证号";
return aCity[parseInt(sId.substr(0,2))]+","+sBirthday+","+(sId.substr(16,1)%2?" 男":"女")
}
document.write(cidInfo("380524198002300016"),"<br/>");
document.write(cidInfo("340524198002300019"),"<br/>")
document.write(cidInfo("340524197711111111"),"<br/>")
document.write(cidInfo("34052419800101001x"),"<br/>");
</script>