phpstudy数据库增删改查登录注册

好的，以下是一个简单的 PHP + MySQL 实现增删改查登录注册的示例：

## 连接数据库

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = mysqli_connect($servername, $username, $password, $dbname);

// 检查连接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

## 插入数据

$sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";

if (mysqli_query($conn, $sql)) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

## 更新数据

$sql = "UPDATE users SET password='$new_password' WHERE username='$username'";

if (mysqli_query($conn, $sql)) {
    echo "Record updated successfully";
} else {
    echo "Error updating record: " . mysqli_error($conn);
}

## 删除数据

$sql = "DELETE FROM users WHERE username='$username'";

if (mysqli_query($conn, $sql)) {
    echo "Record deleted successfully";
} else {
    echo "Error deleting record: " . mysqli_error($conn);
}

## 查询数据

$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 登录成功
} else {
    // 登录失败
}

## 注册

$sql = "SELECT * FROM users WHERE username='$username'";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 用户名已存在
} else {
    $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";

    if (mysqli_query($conn, $sql)) {
        echo "注册成功";
    } else {
        echo "Error: " . $sql . "<br>" . mysqli_error($conn);
    }
}

以上示例仅供参考，实际使用中还需要进行数据过滤和安全性处理。