Server-Side PHP

What is Server-Side Programming?

Server-side programming refers to code that runs on the web server rather than in the user’s browser. When a user visits a website, their browser (client) sends a request to the web server, which processes the request using server-side code and sends back a response.

Client-Side vs Server-Side

Client-Side	Server-Side
Runs in the browser	Runs on the web server
Languages: HTML, CSS, JavaScript	Languages: PHP, Python, Java, Node.js, etc.
Visible to users	Hidden from users
Limited security	More secure
Can’t access databases directly	Direct database access

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PHP as a Server-Side Language

PHP (PHP: Hypertext Preprocessor) is one of the most popular server-side scripting languages. Here’s how it works:

1. Request-Response Cycle

User Browser → Web Server → PHP Engine → Database (if needed) → Response → User Browser

2. PHP Execution Process

1. User requests a PHP page (e.g., example.com/page.php)
2. Web server locates the PHP file
3. PHP engine executes the PHP code
4. PHP generates HTML output
5. Server sends HTML to user’s browser
6. Browser displays the final webpage

3. Key Characteristics

• Dynamic Content: PHP can generate different content based on user input, time, database data, etc.
• Server Processing: All PHP code is processed before reaching the user
• Security: Source code remains hidden from users
• Database Integration: Seamless connection to MySQL, PostgreSQL, and other databases

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What PHP Can Do on the Server

1. Generate Dynamic Web Pages

<?php
$username = "John";
$currentTime = date("Y-m-d H:i:s");
echo "<h1>Welcome, $username!</h1>";
echo "<p>Current time: $currentTime</p>";
?>

2. Database Operations

• Connect to databases (MySQL, PostgreSQL, SQLite)
• Perform CRUD operations (Create, Read, Update, Delete)
• Manage user accounts and data

3. File Management

• Read and write files on the server
• Upload and process user files
• Generate reports and documents

4. Session Management

• Track user login status
• Store temporary data across page visits
• Manage shopping carts and user preferences

5. Form Processing

• Validate user input
• Sanitize data for security
• Send emails and notifications

6. API Integration

• Connect to external services
• Process payments
• Integrate with social media platforms

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Advantages of Server-Side PHP

Security Benefits

• Source code is never exposed to users
• Sensitive operations happen on the server
• Better protection against client-side attacks

Performance

• Powerful server hardware for processing
• Optimized for handling multiple requests
• Efficient database connections

Functionality

• Full access to server resources
• Can perform complex calculations
• Unlimited processing capabilities

Data Management

• Direct database access
• Server-side data validation
• Centralized data processing

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Real-World Examples

E-commerce Website

<?php
// Process user login
if ($_POST['username'] && $_POST['password']) {
    // Validate credentials against database
    $user = authenticateUser($_POST['username'], $_POST['password']);
    if ($user) {
        // Start user session
        session_start();
        $_SESSION['user_id'] = $user['id'];
        header('Location: dashboard.php');
    }
}
?>

Content Management

• WordPress, Drupal use PHP for content management
• Dynamic page generation based on database content
• User role management and permissions

Data Processing

• Form submissions and validation
• File uploads and processing
• Report generation and analytics

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