PHP身份证号验证，并从身份证号提取生日

function getIDCardInfo($IDCard){
if(!eregi("^[1-9]([0-9a-zA-Z]{17}|[0-9a-zA-Z]{14})$",$IDCard)){
echo "格式错误";
$flag=0;
}else{
if(strlen($IDCard)==18){
$tyear=intval(substr($IDCard,6,4));
$tmonth=intval(substr($IDCard,10,2));
$tday=intval(substr($IDCard,12,2));
if($tyear>date("Y")||$tyear<(date("Y")-100)){
$flag=0;

}
elseif($tmonth<0||$tmonth>12){
$flag=0;

}
elseif($tday<0||$tday>31){
$flag=0;

}else{
$tdate=$tyear."-".$tmonth."-".$tday." 00:00:00";
if((time()-mktime(0,0,0,$tmonth,$tday,$tyear))>18*365*24*60*60){
$flag=0;
}else{
$flag=1;
}
}

}elseif(strlen($IDCard)==15){
$tyear=intval("19".substr($IDCard,6,2));
$tmonth=intval(substr($IDCard,8,2));
$tday=intval(substr($IDCard,10,2));
if($tyear>date("Y")||$tyear<(date("Y")-100)){
$flag=0;
}
elseif($tmonth<0||$tmonth>12){
$flag=0;
}
elseif($tday<0||$tday>31){
$flag=0;
}else{
$tdate=$tyear."-".$tmonth."-".$tday." 00:00:00";
if((time()-mktime(0,0,0,$tmonth,$tday,$tyear))>18*365*24*60*60){
$flag=0;
}else{
$flag=1;
}
}
}
}
echo $flag."<br>".$tdate;
}

$flag=1 表示的是１８岁以下的未成年人

＄tdate是生日