<!DOCTYPE html>
<html>
<head>
<title>登录界面</title>
<meta charset="utf-8">
</head>
<body>
<form method="post">
用户名：<input type="text" name="user_name" value=""><input type="submit" name="submit" value="查看用户名是否被占用">
</form>
</body>
</html>
<?php
if (isset($_POST[‘submit‘])) {
$us = $_POST["user_name"];
$conn = mysqli_connect(‘localhost‘,‘root‘)
or die("无法连接到服务器");
mysqli_select_db($conn,‘shiyan‘);
$sql = "select * from student where name=‘$us‘";
$result = mysqli_query($conn,$sql);
$num = mysqli_num_rows($result);
mysqli_close($conn);
if($num >0)
{
echo "<script>alert(‘该用户名已被占用‘);</script>";
}
else
{
echo "<script>alert(‘该用户名未被占用‘);</script>";
}
}
?>
