正则

$username = $_POST['username'];
if(empty($username)){
    echo "<script>alert('姓名不能为空');window.location.href='1.php';</script>";
    die();
}
if(!preg_match('/^[\x{4e00}-\x{9fa5}]{2,4}$/u',$username)){
    echo "<script>alert('姓名格式错误');window.location.href='1.php';</script>";
    die();
}
$mobile = $_POST['mobile'];
if(empty($mobile)){
    echo "<script>alert('手机号不能为空');window.location.href='1.php';</script>";
    die();
}
if(!preg_match('/^1[35789]\d{9}$/',$mobile)){
    echo "<script>alert('手机号格式错误');window.location.href='1.php';</script>";
    die();
}

$email = $_POST['email'];
if(empty($email)){
    echo "<script>alert('邮箱不能为空');window.location.href='1.php';</script>";
    die();
}
if(!preg_match('/^\w+\@\w+\.(com|cn)$/',$email)){
    echo "<script>alert('邮箱格式错误');window.location.href='1.php';</script>";
    die();
}

$idcard = $_POST['idcard'];
if(empty($email)){
    echo "<script>alert('身份证号码不能为空');window.location.href='1.php';</script>";
    die();
}
if(!preg_match('/^\d{17}(x|X|\d)$/',$idcard)){
    echo "<script>alert('身份证格式错误');window.location.href='1.php';</script>";
    die();
}