基础函数

  • mysqli_connect 函数
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mysqli_connect("HOST","username","password","dbname");
//如果使用 sqli_select_db 函数，则最后一个参数可以省略
  • mysqli_select_db 函数
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$conn = mysqli_connect("HOST","username","password");
mysqli_select_db($conn,"dbname");
  • mysqli_query 函数
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$sql = "SELECT * FROM test WHERE ...";
mysqli_query($conn,$sql);
// 会返回执行的结果
  • mysqli_fetch_array 函数
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$reault=mysqli_query();  // 声明一个变量接受sql语句执行的结果
mysqli_fetch_array($result); //将执行的结果提取出来作为一个数组
  • mysqli_num_rows 函数
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mysqli_num_rows($result);
//判断执行结果的行数
  • mysqli_close 函数
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mysqli_close($conn); //关闭mysql连接

登录表单

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<form action="" method="POST">
	<input type="text" name="username"><br />
    <input type="password" name="passwd"><br />
    <input type="submit" value="登录">
</form>
<?php
$username = $_POST['username']; //键值与上面的 name 相对应
$password = $_POST['passwd'];
$sql = "select * from user where username = '$username' and password = '$password'";
//判断用户表中是否有用户输入的用户名和密码
$conn = mysqli_connect("localhost","root","root");
mysqli_select_db($conn,"test"); //此处连接 test 库
$result = mysqli_query($conn,$sql); //执行sql语句
if(mysqli_num_rows($result)){   // 检查是否有返回值，如果结果为空则登录失败
    echo "登录成功";
}
else{
    echo "登录失败";
}
mysqli_close($conn); //关闭连接
?>