$conn = mysql_connect("localhost","","") or die("链接数据库失败");

mysql_select_db("test");

 mysql_query("set names 'utf8'");

    $sql = "INSERT INTO `stu_logon`(`id`, `stuname`, `add`, `age`, `sex`, `fav`) VALUES (NULL,'$name','$add',$age,$sex,'$fav')";

    mysql_query($sql) or die(mysql_error());

 mysql_close($conn);

<?php

if(isset($_GET['stuid'])){//isset的值返回的值是true或false

    $id = $_GET['stuid'];//    form的method有两种：

                       //       post和get(通过url提交)，我们常用的是post

    $conn = mysql_connect("localhost","root","root") or die("链接数据库失败");

    mysql_select_db("test");

    mysql_query("set names 'utf8'");

    $sql = "select * from student where id = $id";

    $result = mysql_query($sql);

    $row = mysql_fetch_array($result);

    echo $row['address'];

}else{

    echo "<script>alert('you dont request this page by url!,please into by A tag');</script>";

}

?>