PHP MySQL 简介 | 菜鸟教程 (runoob.com)

1.编写一个登录界面

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录界面</title>
</head>
<body>

<h1>登录注册系统</h1>
<form action="result.php" method="post">
    <table>
        <tr>
            <td>请输入你的用户名</td>
            <td><input type="text" name="username"></td>
        </tr>
        <tr>
            <td>请输入你的密码</td>
            <td><input type="text" name="password"></td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" name="denglu" value="登录">
                <input type="submit" name="zhuce" value="注册">
            <td>
        </tr>
    </table>
</form>
</body>

2.与mysql建立联系

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<?php
$servername = "localhost";
$username = "你的用户名";
$password = "你的密码";
$dbname="db";  
$conn = new mysqli($servername, $username, $password,$dbname);

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}
echo "连接成功";

line 5：要先在mysql中创建一个名为db(随便)的表，不然会报错

die( ) 输出一条信息，并退出当前脚本

connect_error 返回上一次连接错误的错误描述(报个错)

3.注册

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<?php
$arg1=$_REQUEST['username'];
$arg2=$_REQUEST['password'];
$flag=0;
if($arg1==""||$arg2==""){
    $flag=1;
    $final=1;
 //echo "账户或密码不能为空"."<br/>";
}
else {
    if ($result->num_rows > 0) {
        // 输出数据
        while($row = $result->fetch_assoc()) {
        //查重
            if($arg1==$row["username"]){
                $final=5;
                // echo " 此用户名已存在 " . "<br />";
                break;
            }
        }
    }
}
if(!$flag){

    $sql = "insert into user (username, password)
values ('" . $arg1 . "','" . $arg2 . "')";

    //  echo $sql;
    if ($conn->query($sql) === TRUE) {
        $final=6;
        // echo " 注册成功 " . "<br />";
    } else {
        $final=7;
        // echo "注册失败". "<br />";
    }
}

$result->num_rows 返回结果集中行的数量

$result->fetch_assoc() 从结果集中取得一行作为关联数组

$conn->query($sql) 对数据库进行查询

4.登录

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<?php
//登录
$arg1=$_REQUEST['username'];
$arg2=$_REQUEST['password'];
$flag=0;
if($arg1=="" || $arg2==""){
    $final =1;
  //  echo " 用户名或密码不能为空！ " . "<br />";
}
else if ($result->num_rows > 0) {

    while($row = $result->fetch_assoc()) {
        if($arg1==$row["username"]){
            $flag=1;
            if($arg2==$row["password"]){
                $final =2;
                //echo " 登录成功 " ."<br />";
            }
            else{
                $final =3;
               // echo " 密码错误 " . "<br />";
                break;
            }
        }
    }
    if(!$flag)
        $final =4;
    //echo " 不存在此用户 " . "<br />";
} else {
    $final =4;
   // echo " 不存在此用户 " . "<br />";
}

_REQUEST 收集表单数据

5.将注册和登录结合

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<?php
include ('lianjie.php');
$sql="select username,password from user";
$result=$conn->query($sql);
$final=0;
if(!empty($_REQUEST["zhuce"])){
    include ('zhuce.php');
}
else if(!empty($_REQUEST['denglu'])){
    include("denglu.php");
}
switch ($final) {
    case 0:
        echo " 初始结果 " . "<br />";
        break;
    case 1:
        echo " 用户名或密码不能为空！ " . "<br />";
        break;
    case 2:
        echo " 登录成功 " . "<br />";
        break;
    case 3:
        echo " 密码错误 " . "<br />";
        break;
    case 4:
        echo " 不存在此用户 " . "<br />";
        break;
    case 5:
        echo " 此用户名已存在 " . "<br />";
        break;
    case 6:
        echo " 注册成功 " . "<br />";
        break;
    case 7:
        echo "注册失败" . "<br />" ;
        break;
    default:
        echo " 默认结果 " . "<br />";
        break;
}