Analysis of practical application scenarios of PHP logic

As a popular server-side scripting language, PHP is mainly used to develop web applications. It is flexible and easy to learn, so it has been widely used in various projects. This article will start from actual application scenarios, analyze the use of PHP logic, and provide specific code examples.

1. User login and permission control

In many Web applications, user login and permission control are important functions. User login, user identity verification, and user access to different content can be easily implemented through PHP.

Code example:

<?php
session_start();

if(isset($_POST['username']) && isset($_POST['password'])){
    $username = $_POST['username'];
    $password = $_POST['password'];

    //在实际项目中，这里通常是数据库验证
    if($username == 'admin' && $password == '123456'){
        $_SESSION['user'] = $username;
        header('Location: dashboard.php');
    } else {
        echo '用户名或密码错误';
    }
}
?>

<form action="" method="post">
    <input type="text" name="username" placeholder="用户名">
    <input type="password" name="password" placeholder="密码">
    <input type="submit" value="登录">
</form>

2. Data processing and display

PHP can interact with the database to realize data storage, update, deletion, etc. operate and display the data visually on the page. For example, user information in the database can be queried and displayed on the web page.

Code example:

<?php
//连接数据库
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

//查询用户信息
$sql = "SELECT id, username, email FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - 用户名: " . $row["username"]. " - 邮箱: " . $row["email"]. "<br>";
    }
} else {
    echo "0 结果";
}

$conn->close();
?>

3. Form verification

In web development, forms are a common interaction method, and users can submit data through the form. . PHP can be used to verify form data submitted by users to ensure the legality and security of the data.

Code examples:

<?php
$name = $email = $password = '';

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = test_input($_POST["name"]);
    $email = test_input($_POST["email"]);
    $password = test_input($_POST["password"]);

    //验证邮箱格式
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $emailErr = "无效的邮箱格式";
    }

    //在实际项目中，这里可能会有更多的复杂验证逻辑
}

function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}
?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
    姓名: <input type="text" name="name">
    邮箱: <input type="text" name="email">
    密码: <input type="password" name="password">
    <input type="submit" name="submit" value="提交">
</form>

Through the above three specific application scenario examples, we can see the flexible use of PHP in actual projects. Through logic control, data processing and form validation, PHP helps developers achieve rich functions and interactive effects. I hope these examples can help readers gain a deeper understanding of the practical application of PHP.

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