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When we process the data passed by html on the PHP page, we must first determine whether the data passed is empty and whether the verification code is correct, and then insert the data passed by our html into the database

The code is as follows

<?php
session_start();
header("content-type:text/html;charset=utf-8");
$name=$_POST['name'];
$email=$_POST['email'];
$content=$_POST['content'];
$vcode=$_POST['vcode'];
if($name==''){
    echo "<script>alert('请输入你的姓名');location='" . $_SERVER['HTTP_REFERER'] . "'</script>";
    exit;
}
if($content==''){
    echo "<script>alert('留言内容不能为空');location='" . $_SERVER['HTTP_REFERER'] . "'</script>";
    exit;
}
if($vcode!=$_SESSION['VCODE']){
    echo"<script>alert('你的验证码不正确，请重新输入');location='".$_SERVER['HTTP_REFERER']. "'</script>";
    exit;
}
$conn=mysqli_connect('localhost','root','root','ressage');
mysqli_set_charset($conn,'utf8'); //设定字符集
if($conn){
    $sql=mysqli_prepare($conn,"insert into ressage_user(name,email,content,ressage_time) VALUES (?,?,?,now())");
    $param=mysqli_stmt_bind_param($sql,'sss',$name,$email,$content);
    $result=mysqli_stmt_execute($sql);
if($result){
    echo "<script>alert('留言成功');location.href='ressage.php';</script>";
}else{
    echo"<script>alert('你的留言失败，请稍后重试');location.href='ressage.php';</script>";
    exit;
}
}else{
    die("数据库连接失败".  mysqli_connect_error());
}